diff --git a/.eslintignore b/.eslintignore
index 3ec8e3c394d2..d10aa67a6645 100644
--- a/.eslintignore
+++ b/.eslintignore
@@ -56,14 +56,8 @@ browser/locales/
 # Generated data files
 browser/extensions/formautofill/phonenumberutils/PhoneNumberMetaData.jsm
 
-# devtools/ exclusions
-devtools/client/inspector/markup/test/doc_markup_events_*.html
-devtools/client/performance/components/test/test_jit_optimizations_01.html
-devtools/server/tests/browser/storage-*.html
-!devtools/server/tests/browser/storage-unsecured-iframe.html
-devtools/server/tests/browser/stylesheets-nested-iframes.html
-devtools/client/webreplay/mochitest/examples/*.html
-devtools/client/webreplay/mochitest/examples/
+# Soon to be removed (bug 1609815)
+devtools/client/webreplay/
 
 # Ignore devtools debugger files which aren't intended for linting, and also
 # aren't included in any .eslintignore or .prettierignore file.
diff --git a/devtools/client/inspector/markup/test/browser_markup_events_01.js b/devtools/client/inspector/markup/test/browser_markup_events_01.js
index 87f6ca506553..0939733e4863 100644
--- a/devtools/client/inspector/markup/test/browser_markup_events_01.js
+++ b/devtools/client/inspector/markup/test/browser_markup_events_01.js
@@ -11,7 +11,7 @@ const TEST_URL = URL_ROOT + "doc_markup_events_01.html";
 
 loadHelperScript("helper_events_test_runner.js");
 
-const TEST_DATA = [ // eslint-disable-line
+const TEST_DATA = [
   {
     selector: "html",
     expected: [
@@ -28,12 +28,12 @@ const TEST_DATA = [ // eslint-disable-line
     expected: [
       {
         type: "mouseover",
-        filename: TEST_URL + ":45:31",
+        filename: TEST_URL + ":48:31",
         attributes: ["Capturing", "DOM2"],
         handler:
           "function mouseoverHandler(event) {\n" +
           '  if (event.target.id !== "container") {\n' +
-          '    let output = document.getElementById("output");\n' +
+          '    const output = document.getElementById("output");\n' +
           "    output.textContent = event.target.textContent;\n" +
           "  }\n" +
           "}",
@@ -45,21 +45,21 @@ const TEST_DATA = [ // eslint-disable-line
     expected: [
       {
         type: "click",
-        filename: TEST_URL + ":52:27",
+        filename: TEST_URL + ":55:27",
         attributes: ["Bubbling", "DOM2"],
         handler:
           "function clickHandler(event) {\n" +
-          '  let output = document.getElementById("output");\n' +
+          '  const output = document.getElementById("output");\n' +
           '  output.textContent = "click";\n' +
           "}",
       },
       {
         type: "mouseup",
-        filename: TEST_URL + ":57:29",
+        filename: TEST_URL + ":60:29",
         attributes: ["Bubbling", "DOM2"],
         handler:
           "function mouseupHandler(event) {\n" +
-          '  let output = document.getElementById("output");\n' +
+          '  const output = document.getElementById("output");\n' +
           '  output.textContent = "mouseup";\n' +
           "}",
       },
@@ -81,7 +81,7 @@ const TEST_DATA = [ // eslint-disable-line
     expected: [
       {
         type: "click",
-        filename: TEST_URL + ":72:35",
+        filename: TEST_URL + ":75:35",
         attributes: ["Bubbling", "DOM2"],
         handler:
           "function noeventsClickHandler(event) {\n" +
@@ -117,7 +117,7 @@ const TEST_DATA = [ // eslint-disable-line
     expected: [
       {
         type: "click",
-        filename: TEST_URL + ":67:29",
+        filename: TEST_URL + ":70:29",
         attributes: ["Bubbling", "DOM2"],
         handler: "function(blah) {\n" + '  alert("handleEvent");\n' + "}",
       },
diff --git a/devtools/client/inspector/markup/test/browser_markup_events_02.js b/devtools/client/inspector/markup/test/browser_markup_events_02.js
index f9d017d51a1a..1872f65c2b69 100644
--- a/devtools/client/inspector/markup/test/browser_markup_events_02.js
+++ b/devtools/client/inspector/markup/test/browser_markup_events_02.js
@@ -11,25 +11,25 @@ const TEST_URL = URL_ROOT + "doc_markup_events_02.html";
 
 loadHelperScript("helper_events_test_runner.js");
 
-const TEST_DATA = [ // eslint-disable-line
+const TEST_DATA = [
   {
     selector: "#fatarrow",
     expected: [
       {
         type: "click",
-        filename: TEST_URL + ":39:43",
+        filename: TEST_URL + ":42:43",
         attributes: ["Bubbling", "DOM2"],
         handler: "() => {\n" + '  alert("Fat arrow without params!");\n' + "}",
       },
       {
         type: "click",
-        filename: TEST_URL + ":43:43",
+        filename: TEST_URL + ":46:43",
         attributes: ["Bubbling", "DOM2"],
         handler: "event => {\n" + '  alert("Fat arrow with 1 param!");\n' + "}",
       },
       {
         type: "click",
-        filename: TEST_URL + ":47:43",
+        filename: TEST_URL + ":50:43",
         attributes: ["Bubbling", "DOM2"],
         handler:
           "(event, foo, bar) => {\n" +
@@ -38,7 +38,7 @@ const TEST_DATA = [ // eslint-disable-line
       },
       {
         type: "click",
-        filename: TEST_URL + ":51:43",
+        filename: TEST_URL + ":54:43",
         attributes: ["Bubbling", "DOM2"],
         handler: "b => b",
       },
@@ -49,7 +49,7 @@ const TEST_DATA = [ // eslint-disable-line
     expected: [
       {
         type: "click",
-        filename: TEST_URL + ":62:32",
+        filename: TEST_URL + ":65:32",
         attributes: ["Bubbling", "DOM2"],
         handler: "function(event) {\n" + '  alert("Bound event");\n' + "}",
       },
@@ -60,7 +60,7 @@ const TEST_DATA = [ // eslint-disable-line
     expected: [
       {
         type: "click",
-        filename: TEST_URL + ":85:29",
+        filename: TEST_URL + ":88:29",
         attributes: ["Bubbling", "DOM2"],
         handler: "function() {\n" + '  alert("boundHandleEvent");\n' + "}",
       },
@@ -71,7 +71,7 @@ const TEST_DATA = [ // eslint-disable-line
     expected: [
       {
         type: "click",
-        filename: TEST_URL + ":91:47",
+        filename: TEST_URL + ":94:47",
         attributes: ["Bubbling", "DOM2"],
         handler:
           "function functionProceededByInlineComment() {\n" +
@@ -85,7 +85,7 @@ const TEST_DATA = [ // eslint-disable-line
     expected: [
       {
         type: "click",
-        filename: TEST_URL + ":96:50",
+        filename: TEST_URL + ":99:50",
         attributes: ["Bubbling", "DOM2"],
         handler:
           "function functionProceededByStreamingComment() {\n" +
@@ -99,7 +99,7 @@ const TEST_DATA = [ // eslint-disable-line
     expected: [
       {
         type: "click",
-        filename: TEST_URL + ":71:34",
+        filename: TEST_URL + ":74:34",
         attributes: ["Bubbling", "DOM2"],
         handler: "function() {\n" + '  alert("obj.anonObjectMethod");\n' + "}",
       },
@@ -110,7 +110,7 @@ const TEST_DATA = [ // eslint-disable-line
     expected: [
       {
         type: "click",
-        filename: TEST_URL + ":75:34",
+        filename: TEST_URL + ":78:34",
         attributes: ["Bubbling", "DOM2"],
         handler: "function kay() {\n" + '  alert("obj.objectMethod");\n' + "}",
       },
diff --git a/devtools/client/inspector/markup/test/browser_markup_events_03.js b/devtools/client/inspector/markup/test/browser_markup_events_03.js
index dd75e2e1dcf7..6d4b857db0bd 100644
--- a/devtools/client/inspector/markup/test/browser_markup_events_03.js
+++ b/devtools/client/inspector/markup/test/browser_markup_events_03.js
@@ -11,13 +11,13 @@ const TEST_URL = URL_ROOT + "doc_markup_events_03.html";
 
 loadHelperScript("helper_events_test_runner.js");
 
-const TEST_DATA = [ // eslint-disable-line
+const TEST_DATA = [
   {
     selector: "#es6-method",
     expected: [
       {
         type: "click",
-        filename: TEST_URL + ":66:17",
+        filename: TEST_URL + ":69:17",
         attributes: ["Bubbling", "DOM2"],
         handler:
           "es6Method(foo, bar) {\n" + '  alert("obj.es6Method");\n' + "}",
@@ -29,7 +29,7 @@ const TEST_DATA = [ // eslint-disable-line
     expected: [
       {
         type: "click",
-        filename: TEST_URL + ":85:25",
+        filename: TEST_URL + ":88:25",
         attributes: ["Bubbling", "DOM2"],
         handler: "function* generator() {\n" + '  alert("generator");\n' + "}",
       },
@@ -40,7 +40,7 @@ const TEST_DATA = [ // eslint-disable-line
     expected: [
       {
         type: "click",
-        filename: TEST_URL + ":43:58",
+        filename: TEST_URL + ":46:58",
         attributes: ["Bubbling", "DOM2"],
         handler: "function*() {\n" + '  alert("anonGenerator");\n' + "}",
       },
@@ -51,7 +51,7 @@ const TEST_DATA = [ // eslint-disable-line
     expected: [
       {
         type: "click",
-        filename: TEST_URL + ":20:18",
+        filename: TEST_URL + ":22:18",
         attributes: ["Bubbling", "DOM2"],
         handler:
           "function foo() {\n" + '  alert("namedFunctionExpression");\n' + "}",
@@ -63,7 +63,7 @@ const TEST_DATA = [ // eslint-disable-line
     expected: [
       {
         type: "click",
-        filename: TEST_URL + ":24:43",
+        filename: TEST_URL + ":26:45",
         attributes: ["Bubbling", "DOM2"],
         handler:
           "function() {\n" + '  alert("anonFunctionExpression");\n' + "}",
@@ -75,7 +75,7 @@ const TEST_DATA = [ // eslint-disable-line
     expected: [
       {
         type: "click",
-        filename: TEST_URL + ":29:27",
+        filename: TEST_URL + ":31:27",
         attributes: ["Bubbling", "DOM2"],
         handler: "function bar() {\n" + '  alert("returnedFunction");\n' + "}",
       },
diff --git a/devtools/client/inspector/markup/test/browser_markup_events_04.js b/devtools/client/inspector/markup/test/browser_markup_events_04.js
index 929ad35cb3e8..51ac4faad22c 100644
--- a/devtools/client/inspector/markup/test/browser_markup_events_04.js
+++ b/devtools/client/inspector/markup/test/browser_markup_events_04.js
@@ -11,13 +11,13 @@ const TEST_URL = URL_ROOT + "doc_markup_events_04.html";
 
 loadHelperScript("helper_events_test_runner.js");
 
-const TEST_DATA = [ // eslint-disable-line
+const TEST_DATA = [
   {
     selector: "html",
     expected: [
       {
         type: "click",
-        filename: TEST_URL + ":56:67",
+        filename: TEST_URL + ":59:67",
         attributes: ["Bubbling", "DOM2"],
         handler:
           "function(foo2, bar2) {\n" +
@@ -26,7 +26,7 @@ const TEST_DATA = [ // eslint-disable-line
       },
       {
         type: "click",
-        filename: TEST_URL + ":52:51",
+        filename: TEST_URL + ":55:51",
         attributes: ["Bubbling", "DOM2"],
         handler:
           "function(foo, bar) {\n" +
@@ -71,7 +71,7 @@ const TEST_DATA = [ // eslint-disable-line
     expected: [
       {
         type: "click",
-        filename: TEST_URL + ":24:57",
+        filename: TEST_URL + ":26:47",
         attributes: ["Bubbling", "DOM2"],
         handler:
           "function multi() {\n" + '  alert("multipleAssignment");\n' + "}",
@@ -105,7 +105,7 @@ const TEST_DATA = [ // eslint-disable-line
     expected: [
       {
         type: "click",
-        filename: TEST_URL + ":77:29",
+        filename: TEST_URL + ":80:29",
         attributes: ["Bubbling", "DOM2"],
         handler:
           "function(event) {\n" +
diff --git a/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.0.js b/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.0.js
index b66fdac28a76..eb1b16fa8b2a 100644
--- a/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.0.js
+++ b/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.0.js
@@ -44,41 +44,41 @@ const TEST_DATA = [
       },
       {
         type: "load",
-        filename: TEST_URL + ":27:38",
+        filename: TEST_URL + ":29:38",
         attributes: [
           "Bubbling",
           "DOM2"
         ],
         handler: `
           () => {
-            var handler1 = function liveDivDblClick() {
+            const handler1 = function liveDivDblClick() {
               alert(1);
             };
-            var handler2 = function liveDivDragStart() {
+            const handler2 = function liveDivDragStart() {
               alert(2);
             };
-            var handler3 = function liveDivDragLeave() {
+            const handler3 = function liveDivDragLeave() {
               alert(3);
             };
-            var handler4 = function liveDivDragEnd() {
+            const handler4 = function liveDivDragEnd() {
               alert(4);
             };
-            var handler5 = function liveDivDrop() {
+            const handler5 = function liveDivDrop() {
               alert(5);
             };
-            var handler6 = function liveDivDragOver() {
+            const handler6 = function liveDivDragOver() {
               alert(6);
             };
-            var handler7 = function divClick1() {
+            const handler7 = function divClick1() {
               alert(7);
             };
-            var handler8 = function divClick2() {
+            const handler8 = function divClick2() {
               alert(8);
             };
-            var handler9 = function divKeyDown() {
+            const handler9 = function divKeyDown() {
               alert(9);
             };
-            var handler10 = function divDragOut() {
+            const handler10 = function divDragOut() {
               alert(10);
             };
 
@@ -98,7 +98,7 @@ const TEST_DATA = [
               $(document).on("dragout", "#livediv:xxxxx", handler10);
             }
 
-            var div = $("div")[0];
+            const div = $("div")[0];
             $(div).click(handler7);
             $(div).click(handler8);
             $(div).keydown(handler9);
@@ -142,7 +142,7 @@ const TEST_DATA = [
     expected: [
       {
         type: "click",
-        filename: TEST_URL + ":34:41",
+        filename: TEST_URL + ":36:43",
         attributes: [
           "jQuery"
         ],
@@ -153,7 +153,7 @@ const TEST_DATA = [
       },
       {
         type: "click",
-        filename: TEST_URL + ":35:41",
+        filename: TEST_URL + ":37:43",
         attributes: [
           "jQuery"
         ],
@@ -195,7 +195,7 @@ const TEST_DATA = [
       },
       {
         type: "keydown",
-        filename: TEST_URL + ":36:42",
+        filename: TEST_URL + ":38:44",
         attributes: [
           "jQuery"
         ],
diff --git a/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.1.js b/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.1.js
index dbde921ea649..e98ed89439f0 100644
--- a/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.1.js
+++ b/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.1.js
@@ -18,41 +18,41 @@ const TEST_DATA = [
     expected: [
       {
         type: "load",
-        filename: TEST_URL + ":27:38",
+        filename: TEST_URL + ":29:38",
         attributes: [
           "Bubbling",
           "DOM2"
         ],
         handler: `
           () => {
-            var handler1 = function liveDivDblClick() {
+            const handler1 = function liveDivDblClick() {
               alert(1);
             };
-            var handler2 = function liveDivDragStart() {
+            const handler2 = function liveDivDragStart() {
               alert(2);
             };
-            var handler3 = function liveDivDragLeave() {
+            const handler3 = function liveDivDragLeave() {
               alert(3);
             };
-            var handler4 = function liveDivDragEnd() {
+            const handler4 = function liveDivDragEnd() {
               alert(4);
             };
-            var handler5 = function liveDivDrop() {
+            const handler5 = function liveDivDrop() {
               alert(5);
             };
-            var handler6 = function liveDivDragOver() {
+            const handler6 = function liveDivDragOver() {
               alert(6);
             };
-            var handler7 = function divClick1() {
+            const handler7 = function divClick1() {
               alert(7);
             };
-            var handler8 = function divClick2() {
+            const handler8 = function divClick2() {
               alert(8);
             };
-            var handler9 = function divKeyDown() {
+            const handler9 = function divKeyDown() {
               alert(9);
             };
-            var handler10 = function divDragOut() {
+            const handler10 = function divDragOut() {
               alert(10);
             };
 
@@ -72,7 +72,7 @@ const TEST_DATA = [
               $(document).on("dragout", "#livediv:xxxxx", handler10);
             }
 
-            var div = $("div")[0];
+            const div = $("div")[0];
             $(div).click(handler7);
             $(div).click(handler8);
             $(div).keydown(handler9);
@@ -126,7 +126,7 @@ const TEST_DATA = [
     expected: [
       {
         type: "click",
-        filename: TEST_URL + ":34:41",
+        filename: TEST_URL + ":36:43",
         attributes: [
           "jQuery"
         ],
@@ -137,7 +137,7 @@ const TEST_DATA = [
       },
       {
         type: "click",
-        filename: TEST_URL + ":35:41",
+        filename: TEST_URL + ":37:43",
         attributes: [
           "jQuery"
         ],
@@ -189,7 +189,7 @@ const TEST_DATA = [
       },
       {
         type: "keydown",
-        filename: TEST_URL + ":36:42",
+        filename: TEST_URL + ":38:44",
         attributes: [
           "jQuery"
         ],
diff --git a/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.11.1.js b/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.11.1.js
index 3baef3f6a81d..1a5303dfff1c 100644
--- a/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.11.1.js
+++ b/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.11.1.js
@@ -18,41 +18,41 @@ const TEST_DATA = [
     expected: [
       {
         type: "load",
-        filename: TEST_URL + ":27:38",
+        filename: TEST_URL + ":29:38",
         attributes: [
           "Bubbling",
           "DOM2"
         ],
         handler: `
           () => {
-            var handler1 = function liveDivDblClick() {
+            const handler1 = function liveDivDblClick() {
               alert(1);
             };
-            var handler2 = function liveDivDragStart() {
+            const handler2 = function liveDivDragStart() {
               alert(2);
             };
-            var handler3 = function liveDivDragLeave() {
+            const handler3 = function liveDivDragLeave() {
               alert(3);
             };
-            var handler4 = function liveDivDragEnd() {
+            const handler4 = function liveDivDragEnd() {
               alert(4);
             };
-            var handler5 = function liveDivDrop() {
+            const handler5 = function liveDivDrop() {
               alert(5);
             };
-            var handler6 = function liveDivDragOver() {
+            const handler6 = function liveDivDragOver() {
               alert(6);
             };
-            var handler7 = function divClick1() {
+            const handler7 = function divClick1() {
               alert(7);
             };
-            var handler8 = function divClick2() {
+            const handler8 = function divClick2() {
               alert(8);
             };
-            var handler9 = function divKeyDown() {
+            const handler9 = function divKeyDown() {
               alert(9);
             };
-            var handler10 = function divDragOut() {
+            const handler10 = function divDragOut() {
               alert(10);
             };
 
@@ -72,7 +72,7 @@ const TEST_DATA = [
               $(document).on("dragout", "#livediv:xxxxx", handler10);
             }
 
-            var div = $("div")[0];
+            const div = $("div")[0];
             $(div).click(handler7);
             $(div).click(handler8);
             $(div).keydown(handler9);
@@ -86,7 +86,7 @@ const TEST_DATA = [
     expected: [
       {
         type: "click",
-        filename: TEST_URL + ":34:41",
+        filename: TEST_URL + ":36:43",
         attributes: [
           "jQuery"
         ],
@@ -97,7 +97,7 @@ const TEST_DATA = [
       },
       {
         type: "click",
-        filename: TEST_URL + ":35:41",
+        filename: TEST_URL + ":37:43",
         attributes: [
           "jQuery"
         ],
@@ -108,7 +108,7 @@ const TEST_DATA = [
       },
       {
         type: "keydown",
-        filename: TEST_URL + ":36:42",
+        filename: TEST_URL + ":38:44",
         attributes: [
           "jQuery"
         ],
@@ -125,7 +125,7 @@ const TEST_DATA = [
     expected: [
       {
         type: "dragend",
-        filename: TEST_URL + ":31:46",
+        filename: TEST_URL + ":33:48",
         attributes: [
           "jQuery",
           "Live"
@@ -137,7 +137,7 @@ const TEST_DATA = [
       },
       {
         type: "dragleave",
-        filename: TEST_URL + ":30:48",
+        filename: TEST_URL + ":32:50",
         attributes: [
           "jQuery",
           "Live"
@@ -149,7 +149,7 @@ const TEST_DATA = [
       },
       {
         type: "dragover",
-        filename: TEST_URL + ":33:47",
+        filename: TEST_URL + ":35:49",
         attributes: [
           "jQuery",
           "Live"
@@ -161,7 +161,7 @@ const TEST_DATA = [
       },
       {
         type: "drop",
-        filename: TEST_URL + ":32:43",
+        filename: TEST_URL + ":34:45",
         attributes: [
           "jQuery",
           "Live"
diff --git a/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.2.js b/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.2.js
index 5062b8325c40..57f522b8f8f4 100644
--- a/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.2.js
+++ b/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.2.js
@@ -18,41 +18,41 @@ const TEST_DATA = [
     expected: [
       {
         type: "load",
-        filename: TEST_URL + ":27:38",
+        filename: TEST_URL + ":29:38",
         attributes: [
           "Bubbling",
           "DOM2"
         ],
         handler: `
           () => {
-            var handler1 = function liveDivDblClick() {
+            const handler1 = function liveDivDblClick() {
               alert(1);
             };
-            var handler2 = function liveDivDragStart() {
+            const handler2 = function liveDivDragStart() {
               alert(2);
             };
-            var handler3 = function liveDivDragLeave() {
+            const handler3 = function liveDivDragLeave() {
               alert(3);
             };
-            var handler4 = function liveDivDragEnd() {
+            const handler4 = function liveDivDragEnd() {
               alert(4);
             };
-            var handler5 = function liveDivDrop() {
+            const handler5 = function liveDivDrop() {
               alert(5);
             };
-            var handler6 = function liveDivDragOver() {
+            const handler6 = function liveDivDragOver() {
               alert(6);
             };
-            var handler7 = function divClick1() {
+            const handler7 = function divClick1() {
               alert(7);
             };
-            var handler8 = function divClick2() {
+            const handler8 = function divClick2() {
               alert(8);
             };
-            var handler9 = function divKeyDown() {
+            const handler9 = function divKeyDown() {
               alert(9);
             };
-            var handler10 = function divDragOut() {
+            const handler10 = function divDragOut() {
               alert(10);
             };
 
@@ -72,7 +72,7 @@ const TEST_DATA = [
               $(document).on("dragout", "#livediv:xxxxx", handler10);
             }
 
-            var div = $("div")[0];
+            const div = $("div")[0];
             $(div).click(handler7);
             $(div).click(handler8);
             $(div).keydown(handler9);
@@ -85,7 +85,7 @@ const TEST_DATA = [
     expected: [
       {
         type: "click",
-        filename: TEST_URL + ":34:41",
+        filename: TEST_URL + ":36:43",
         attributes: [
           "jQuery"
         ],
@@ -96,7 +96,7 @@ const TEST_DATA = [
       },
       {
         type: "click",
-        filename: TEST_URL + ":35:41",
+        filename: TEST_URL + ":37:43",
         attributes: [
           "jQuery"
         ],
@@ -122,7 +122,7 @@ const TEST_DATA = [
       },
       {
         type: "keydown",
-        filename: TEST_URL + ":36:42",
+        filename: TEST_URL + ":38:44",
         attributes: [
           "jQuery"
         ],
diff --git a/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.3.js b/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.3.js
index c1bcf5823ad9..b7939c069bce 100644
--- a/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.3.js
+++ b/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.3.js
@@ -31,41 +31,41 @@ const TEST_DATA = [
       },
       {
         type: "load",
-        filename: TEST_URL + ":27:38",
+        filename: TEST_URL + ":29:38",
         attributes: [
           "Bubbling",
           "DOM2"
         ],
         handler: `
           () => {
-            var handler1 = function liveDivDblClick() {
+            const handler1 = function liveDivDblClick() {
               alert(1);
             };
-            var handler2 = function liveDivDragStart() {
+            const handler2 = function liveDivDragStart() {
               alert(2);
             };
-            var handler3 = function liveDivDragLeave() {
+            const handler3 = function liveDivDragLeave() {
               alert(3);
             };
-            var handler4 = function liveDivDragEnd() {
+            const handler4 = function liveDivDragEnd() {
               alert(4);
             };
-            var handler5 = function liveDivDrop() {
+            const handler5 = function liveDivDrop() {
               alert(5);
             };
-            var handler6 = function liveDivDragOver() {
+            const handler6 = function liveDivDragOver() {
               alert(6);
             };
-            var handler7 = function divClick1() {
+            const handler7 = function divClick1() {
               alert(7);
             };
-            var handler8 = function divClick2() {
+            const handler8 = function divClick2() {
               alert(8);
             };
-            var handler9 = function divKeyDown() {
+            const handler9 = function divKeyDown() {
               alert(9);
             };
-            var handler10 = function divDragOut() {
+            const handler10 = function divDragOut() {
               alert(10);
             };
 
@@ -85,7 +85,7 @@ const TEST_DATA = [
               $(document).on("dragout", "#livediv:xxxxx", handler10);
             }
 
-            var div = $("div")[0];
+            const div = $("div")[0];
             $(div).click(handler7);
             $(div).click(handler8);
             $(div).keydown(handler9);
@@ -98,7 +98,7 @@ const TEST_DATA = [
     expected: [
       {
         type: "click",
-        filename: TEST_URL + ":34:41",
+        filename: TEST_URL + ":36:43",
         attributes: [
           "jQuery"
         ],
@@ -109,7 +109,7 @@ const TEST_DATA = [
       },
       {
         type: "click",
-        filename: TEST_URL + ":35:41",
+        filename: TEST_URL + ":37:43",
         attributes: [
           "jQuery"
         ],
@@ -120,7 +120,7 @@ const TEST_DATA = [
       },
       {
         type: "keydown",
-        filename: TEST_URL + ":36:42",
+        filename: TEST_URL + ":38:44",
         attributes: [
           "jQuery"
         ],
@@ -136,7 +136,7 @@ const TEST_DATA = [
     expected: [
       {
         type: "dblclick",
-        filename: TEST_URL + ":28:47",
+        filename: TEST_URL + ":30:49",
         attributes: [
           "jQuery",
           "Live"
@@ -148,7 +148,7 @@ const TEST_DATA = [
       },
       {
         type: "dragstart",
-        filename: TEST_URL + ":29:48",
+        filename: TEST_URL + ":31:50",
         attributes: [
           "jQuery",
           "Live"
diff --git a/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.4.js b/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.4.js
index a774252fb9c0..d0ea6fa36cce 100644
--- a/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.4.js
+++ b/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.4.js
@@ -31,41 +31,41 @@ const TEST_DATA = [
       },
       {
         type: "load",
-        filename: TEST_URL + ":27:38",
+        filename: TEST_URL + ":29:38",
         attributes: [
           "Bubbling",
           "DOM2"
         ],
         handler: `
           () => {
-            var handler1 = function liveDivDblClick() {
+            const handler1 = function liveDivDblClick() {
               alert(1);
             };
-            var handler2 = function liveDivDragStart() {
+            const handler2 = function liveDivDragStart() {
               alert(2);
             };
-            var handler3 = function liveDivDragLeave() {
+            const handler3 = function liveDivDragLeave() {
               alert(3);
             };
-            var handler4 = function liveDivDragEnd() {
+            const handler4 = function liveDivDragEnd() {
               alert(4);
             };
-            var handler5 = function liveDivDrop() {
+            const handler5 = function liveDivDrop() {
               alert(5);
             };
-            var handler6 = function liveDivDragOver() {
+            const handler6 = function liveDivDragOver() {
               alert(6);
             };
-            var handler7 = function divClick1() {
+            const handler7 = function divClick1() {
               alert(7);
             };
-            var handler8 = function divClick2() {
+            const handler8 = function divClick2() {
               alert(8);
             };
-            var handler9 = function divKeyDown() {
+            const handler9 = function divKeyDown() {
               alert(9);
             };
-            var handler10 = function divDragOut() {
+            const handler10 = function divDragOut() {
               alert(10);
             };
 
@@ -85,7 +85,7 @@ const TEST_DATA = [
               $(document).on("dragout", "#livediv:xxxxx", handler10);
             }
 
-            var div = $("div")[0];
+            const div = $("div")[0];
             $(div).click(handler7);
             $(div).click(handler8);
             $(div).keydown(handler9);
@@ -118,7 +118,7 @@ const TEST_DATA = [
     expected: [
       {
         type: "click",
-        filename: TEST_URL + ":34:41",
+        filename: TEST_URL + ":36:43",
         attributes: [
           "jQuery"
         ],
@@ -129,7 +129,7 @@ const TEST_DATA = [
       },
       {
         type: "click",
-        filename: TEST_URL + ":35:41",
+        filename: TEST_URL + ":37:43",
         attributes: [
           "jQuery"
         ],
@@ -140,7 +140,7 @@ const TEST_DATA = [
       },
       {
         type: "keydown",
-        filename: TEST_URL + ":36:42",
+        filename: TEST_URL + ":38:44",
         attributes: [
           "jQuery"
         ],
@@ -156,7 +156,7 @@ const TEST_DATA = [
     expected: [
       {
         type: "dblclick",
-        filename: TEST_URL + ":28:47",
+        filename: TEST_URL + ":30:49",
         attributes: [
           "jQuery",
           "Live"
@@ -180,7 +180,7 @@ const TEST_DATA = [
       },
       {
         type: "dragstart",
-        filename: TEST_URL + ":29:48",
+        filename: TEST_URL + ":31:50",
         attributes: [
           "jQuery",
           "Live"
diff --git a/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.6.js b/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.6.js
index c4bf82c2cf2e..4ae38a3a488d 100644
--- a/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.6.js
+++ b/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.6.js
@@ -32,41 +32,41 @@ const TEST_DATA = [
       },
       {
         type: "load",
-        filename: TEST_URL + ":27:38",
+        filename: TEST_URL + ":29:38",
         attributes: [
           "Bubbling",
           "DOM2"
         ],
         handler: `
           () => {
-            var handler1 = function liveDivDblClick() {
+            const handler1 = function liveDivDblClick() {
               alert(1);
             };
-            var handler2 = function liveDivDragStart() {
+            const handler2 = function liveDivDragStart() {
               alert(2);
             };
-            var handler3 = function liveDivDragLeave() {
+            const handler3 = function liveDivDragLeave() {
               alert(3);
             };
-            var handler4 = function liveDivDragEnd() {
+            const handler4 = function liveDivDragEnd() {
               alert(4);
             };
-            var handler5 = function liveDivDrop() {
+            const handler5 = function liveDivDrop() {
               alert(5);
             };
-            var handler6 = function liveDivDragOver() {
+            const handler6 = function liveDivDragOver() {
               alert(6);
             };
-            var handler7 = function divClick1() {
+            const handler7 = function divClick1() {
               alert(7);
             };
-            var handler8 = function divClick2() {
+            const handler8 = function divClick2() {
               alert(8);
             };
-            var handler9 = function divKeyDown() {
+            const handler9 = function divKeyDown() {
               alert(9);
             };
-            var handler10 = function divDragOut() {
+            const handler10 = function divDragOut() {
               alert(10);
             };
 
@@ -86,7 +86,7 @@ const TEST_DATA = [
               $(document).on("dragout", "#livediv:xxxxx", handler10);
             }
 
-            var div = $("div")[0];
+            const div = $("div")[0];
             $(div).click(handler7);
             $(div).click(handler8);
             $(div).keydown(handler9);
@@ -116,7 +116,7 @@ const TEST_DATA = [
     expected: [
       {
         type: "click",
-        filename: TEST_URL + ":34:41",
+        filename: TEST_URL + ":36:43",
         attributes: [
           "jQuery"
         ],
@@ -127,7 +127,7 @@ const TEST_DATA = [
       },
       {
         type: "click",
-        filename: TEST_URL + ":35:41",
+        filename: TEST_URL + ":37:43",
         attributes: [
           "jQuery"
         ],
@@ -138,7 +138,7 @@ const TEST_DATA = [
       },
       {
         type: "keydown",
-        filename: TEST_URL + ":36:42",
+        filename: TEST_URL + ":38:44",
         attributes: [
           "jQuery"
         ],
@@ -154,7 +154,7 @@ const TEST_DATA = [
     expected: [
       {
         type: "dblclick",
-        filename: TEST_URL + ":28:47",
+        filename: TEST_URL + ":30:49",
         attributes: [
           "jQuery",
           "Live"
@@ -211,7 +211,7 @@ const TEST_DATA = [
       },
       {
         type: "dragend",
-        filename: TEST_URL + ":31:46",
+        filename: TEST_URL + ":33:48",
         attributes: [
           "jQuery",
           "Live"
@@ -268,7 +268,7 @@ const TEST_DATA = [
       },
       {
         type: "dragleave",
-        filename: TEST_URL + ":30:48",
+        filename: TEST_URL + ":32:50",
         attributes: [
           "jQuery",
           "Live"
@@ -325,7 +325,7 @@ const TEST_DATA = [
       },
       {
         type: "dragstart",
-        filename: TEST_URL + ":29:48",
+        filename: TEST_URL + ":31:50",
         attributes: [
           "jQuery",
           "Live"
diff --git a/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.7.js b/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.7.js
index 296e8d805277..0ecebfd4f0f2 100644
--- a/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.7.js
+++ b/devtools/client/inspector/markup/test/browser_markup_events_jquery_1.7.js
@@ -32,41 +32,41 @@ const TEST_DATA = [
       },
       {
         type: "load",
-        filename: TEST_URL + ":27:38",
+        filename: TEST_URL + ":29:38",
         attributes: [
           "Bubbling",
           "DOM2"
         ],
         handler: `
           () => {
-            var handler1 = function liveDivDblClick() {
+            const handler1 = function liveDivDblClick() {
               alert(1);
             };
-            var handler2 = function liveDivDragStart() {
+            const handler2 = function liveDivDragStart() {
               alert(2);
             };
-            var handler3 = function liveDivDragLeave() {
+            const handler3 = function liveDivDragLeave() {
               alert(3);
             };
-            var handler4 = function liveDivDragEnd() {
+            const handler4 = function liveDivDragEnd() {
               alert(4);
             };
-            var handler5 = function liveDivDrop() {
+            const handler5 = function liveDivDrop() {
               alert(5);
             };
-            var handler6 = function liveDivDragOver() {
+            const handler6 = function liveDivDragOver() {
               alert(6);
             };
-            var handler7 = function divClick1() {
+            const handler7 = function divClick1() {
               alert(7);
             };
-            var handler8 = function divClick2() {
+            const handler8 = function divClick2() {
               alert(8);
             };
-            var handler9 = function divKeyDown() {
+            const handler9 = function divKeyDown() {
               alert(9);
             };
-            var handler10 = function divDragOut() {
+            const handler10 = function divDragOut() {
               alert(10);
             };
 
@@ -86,7 +86,7 @@ const TEST_DATA = [
               $(document).on("dragout", "#livediv:xxxxx", handler10);
             }
 
-            var div = $("div")[0];
+            const div = $("div")[0];
             $(div).click(handler7);
             $(div).click(handler8);
             $(div).keydown(handler9);
@@ -116,7 +116,7 @@ const TEST_DATA = [
     expected: [
       {
         type: "click",
-        filename: TEST_URL + ":34:41",
+        filename: TEST_URL + ":36:43",
         attributes: [
           "jQuery"
         ],
@@ -127,7 +127,7 @@ const TEST_DATA = [
       },
       {
         type: "click",
-        filename: TEST_URL + ":35:41",
+        filename: TEST_URL + ":37:43",
         attributes: [
           "jQuery"
         ],
@@ -138,7 +138,7 @@ const TEST_DATA = [
       },
       {
         type: "keydown",
-        filename: TEST_URL + ":36:42",
+        filename: TEST_URL + ":38:44",
         attributes: [
           "jQuery"
         ],
@@ -154,7 +154,7 @@ const TEST_DATA = [
     expected: [
       {
         type: "dblclick",
-        filename: TEST_URL + ":28:47",
+        filename: TEST_URL + ":30:49",
         attributes: [
           "jQuery",
           "Live"
@@ -166,7 +166,7 @@ const TEST_DATA = [
       },
       {
         type: "dragend",
-        filename: TEST_URL + ":31:46",
+        filename: TEST_URL + ":33:48",
         attributes: [
           "jQuery",
           "Live"
@@ -178,7 +178,7 @@ const TEST_DATA = [
       },
       {
         type: "dragleave",
-        filename: TEST_URL + ":30:48",
+        filename: TEST_URL + ":32:50",
         attributes: [
           "jQuery",
           "Live"
@@ -190,7 +190,7 @@ const TEST_DATA = [
       },
       {
         type: "dragover",
-        filename: TEST_URL + ":33:47",
+        filename: TEST_URL + ":35:49",
         attributes: [
           "jQuery",
           "Live"
@@ -202,7 +202,7 @@ const TEST_DATA = [
       },
       {
         type: "dragstart",
-        filename: TEST_URL + ":29:48",
+        filename: TEST_URL + ":31:50",
         attributes: [
           "jQuery",
           "Live"
@@ -214,7 +214,7 @@ const TEST_DATA = [
       },
       {
         type: "drop",
-        filename: TEST_URL + ":32:43",
+        filename: TEST_URL + ":34:45",
         attributes: [
           "jQuery",
           "Live"
diff --git a/devtools/client/inspector/markup/test/browser_markup_events_jquery_2.1.1.js b/devtools/client/inspector/markup/test/browser_markup_events_jquery_2.1.1.js
index aa4ce2b271ec..fcc2f9b81ffc 100644
--- a/devtools/client/inspector/markup/test/browser_markup_events_jquery_2.1.1.js
+++ b/devtools/client/inspector/markup/test/browser_markup_events_jquery_2.1.1.js
@@ -20,41 +20,41 @@ const TEST_DATA = [
     expected: [
       {
         type: "load",
-        filename: TEST_URL + ":27:38",
+        filename: TEST_URL + ":29:38",
         attributes: [
           "Bubbling",
           "DOM2"
         ],
         handler: `
           () => {
-            var handler1 = function liveDivDblClick() {
+            const handler1 = function liveDivDblClick() {
               alert(1);
             };
-            var handler2 = function liveDivDragStart() {
+            const handler2 = function liveDivDragStart() {
               alert(2);
             };
-            var handler3 = function liveDivDragLeave() {
+            const handler3 = function liveDivDragLeave() {
               alert(3);
             };
-            var handler4 = function liveDivDragEnd() {
+            const handler4 = function liveDivDragEnd() {
               alert(4);
             };
-            var handler5 = function liveDivDrop() {
+            const handler5 = function liveDivDrop() {
               alert(5);
             };
-            var handler6 = function liveDivDragOver() {
+            const handler6 = function liveDivDragOver() {
               alert(6);
             };
-            var handler7 = function divClick1() {
+            const handler7 = function divClick1() {
               alert(7);
             };
-            var handler8 = function divClick2() {
+            const handler8 = function divClick2() {
               alert(8);
             };
-            var handler9 = function divKeyDown() {
+            const handler9 = function divKeyDown() {
               alert(9);
             };
-            var handler10 = function divDragOut() {
+            const handler10 = function divDragOut() {
               alert(10);
             };
 
@@ -74,7 +74,7 @@ const TEST_DATA = [
               $(document).on("dragout", "#livediv:xxxxx", handler10);
             }
 
-            var div = $("div")[0];
+            const div = $("div")[0];
             $(div).click(handler7);
             $(div).click(handler8);
             $(div).keydown(handler9);
@@ -87,7 +87,7 @@ const TEST_DATA = [
     expected: [
       {
         type: "click",
-        filename: TEST_URL + ":34:41",
+        filename: TEST_URL + ":36:43",
         attributes: [
           "jQuery"
         ],
@@ -98,7 +98,7 @@ const TEST_DATA = [
       },
       {
         type: "click",
-        filename: TEST_URL + ":35:41",
+        filename: TEST_URL + ":37:43",
         attributes: [
           "jQuery"
         ],
@@ -109,7 +109,7 @@ const TEST_DATA = [
       },
       {
         type: "keydown",
-        filename: TEST_URL + ":36:42",
+        filename: TEST_URL + ":38:44",
         attributes: [
           "jQuery"
         ],
@@ -125,7 +125,7 @@ const TEST_DATA = [
     expected: [
       {
         type: "dragend",
-        filename: TEST_URL + ":31:46",
+        filename: TEST_URL + ":33:48",
         attributes: [
           "jQuery",
           "Live"
@@ -137,7 +137,7 @@ const TEST_DATA = [
       },
       {
         type: "dragleave",
-        filename: TEST_URL + ":30:48",
+        filename: TEST_URL + ":32:50",
         attributes: [
           "jQuery",
           "Live"
@@ -149,7 +149,7 @@ const TEST_DATA = [
       },
       {
         type: "dragover",
-        filename: TEST_URL + ":33:47",
+        filename: TEST_URL + ":35:49",
         attributes: [
           "jQuery",
           "Live"
@@ -161,7 +161,7 @@ const TEST_DATA = [
       },
       {
         type: "drop",
-        filename: TEST_URL + ":32:43",
+        filename: TEST_URL + ":34:45",
         attributes: [
           "jQuery",
           "Live"
diff --git a/devtools/client/inspector/markup/test/browser_markup_events_object_listener.js b/devtools/client/inspector/markup/test/browser_markup_events_object_listener.js
index cc140dddf596..3173f8dbbd18 100644
--- a/devtools/client/inspector/markup/test/browser_markup_events_object_listener.js
+++ b/devtools/client/inspector/markup/test/browser_markup_events_object_listener.js
@@ -18,7 +18,7 @@ const TEST_DATA = [ // eslint-disable-line
     expected: [
       {
         type: "click",
-        filename: TEST_URL + ":17:23",
+        filename: TEST_URL + ":20:23",
         attributes: ["Bubbling", "DOM2"],
         handler: `() => {\n` + `  console.log("handleEvent");\n` + `}`,
       },
@@ -29,7 +29,7 @@ const TEST_DATA = [ // eslint-disable-line
     expected: [
       {
         type: "click",
-        filename: TEST_URL + ":24:23",
+        filename: TEST_URL + ":27:23",
         attributes: ["Bubbling", "DOM2"],
         handler: `() => {\n` + `  console.log("handleEvent");\n` + `}`,
       },
diff --git a/devtools/client/inspector/markup/test/doc_markup_events_01.html b/devtools/client/inspector/markup/test/doc_markup_events_01.html
index 4d848bc95b35..be7cfb43a077 100644
--- a/devtools/client/inspector/markup/test/doc_markup_events_01.html
+++ b/devtools/client/inspector/markup/test/doc_markup_events_01.html
@@ -29,6 +29,9 @@
     }
     </style>
     <script type="application/javascript">
+      "use strict";
+
+      /* exported init */
       function init() {
         const container = document.getElementById("container");
         const multiple = document.getElementById("multiple");
@@ -37,7 +40,7 @@
         multiple.addEventListener("click", clickHandler);
         multiple.addEventListener("mouseup", mouseupHandler);
 
-        const he = new handleEventClick();
+        const he = new HandleEventClick();
         const handleevent = document.getElementById("handleevent");
         handleevent.addEventListener("click", he);
       }
@@ -59,11 +62,11 @@
         output.textContent = "mouseup";
       }
 
-      function handleEventClick(hehe) {
+      function HandleEventClick(hehe) {
 
       }
 
-      handleEventClick.prototype = {
+      HandleEventClick.prototype = {
         handleEvent: function(blah) {
           alert("handleEvent");
         }
@@ -73,6 +76,7 @@
         alert("noevents has an event listener");
       }
 
+      /* exported addNoeventsClickHandler, removeNoeventsClickHandler */
       function addNoeventsClickHandler() {
         const noevents = document.getElementById("noevents");
         noevents.addEventListener("click", noeventsClickHandler);
diff --git a/devtools/client/inspector/markup/test/doc_markup_events_02.html b/devtools/client/inspector/markup/test/doc_markup_events_02.html
index 4e8f839cfdd0..d22b3d4d3f4b 100644
--- a/devtools/client/inspector/markup/test/doc_markup_events_02.html
+++ b/devtools/client/inspector/markup/test/doc_markup_events_02.html
@@ -17,24 +17,27 @@
     }
     </style>
     <script type="application/javascript">
+      "use strict";
+
+      /* exported init */
       function init() {
         const fatarrow = document.getElementById("fatarrow");
 
-        const he = new handleEventClick();
+        const he = new HandleEventClick();
         const anonObjectMethod = document.getElementById("anon-object-method");
         anonObjectMethod.addEventListener("click", he.anonObjectMethod);
 
         const objectMethod = document.getElementById("object-method");
         objectMethod.addEventListener("click", he.objectMethod);
 
-        const bhe = new boundHandleEventClick();
+        const bhe = new BoundHandleEventClick();
         const boundheNode = document.getElementById("boundhe");
         bhe.handleEvent = bhe.handleEvent.bind(bhe);
         boundheNode.addEventListener("click", bhe);
 
         const boundNode = document.getElementById("bound");
-        boundClickHandler = boundClickHandler.bind(this);
-        boundNode.addEventListener("click", boundClickHandler);
+        BoundClickHandler = BoundClickHandler.bind(this);
+        boundNode.addEventListener("click", BoundClickHandler);
 
         fatarrow.addEventListener("click", () => {
           alert("Fat arrow without params!");
@@ -59,15 +62,15 @@
           .addEventListener("click", functionProceededByStreamingComment);
       }
 
-      function boundClickHandler(event) {
+      function BoundClickHandler(event) {
         alert("Bound event");
       }
 
-      function handleEventClick(hehe) {
+      function HandleEventClick(hehe) {
 
       }
 
-      handleEventClick.prototype = {
+      HandleEventClick.prototype = {
         anonObjectMethod: function() {
           alert("obj.anonObjectMethod");
         },
@@ -77,11 +80,11 @@
         },
       };
 
-      function boundHandleEventClick() {
+      function BoundHandleEventClick() {
 
       }
 
-      boundHandleEventClick.prototype = {
+      BoundHandleEventClick.prototype = {
         handleEvent: function() {
           alert("boundHandleEvent");
         }
diff --git a/devtools/client/inspector/markup/test/doc_markup_events_03.html b/devtools/client/inspector/markup/test/doc_markup_events_03.html
index edf9a83b117a..15c02d4bb554 100644
--- a/devtools/client/inspector/markup/test/doc_markup_events_03.html
+++ b/devtools/client/inspector/markup/test/doc_markup_events_03.html
@@ -16,6 +16,8 @@
     }
     </style>
     <script type="application/javascript">
+      "use strict";
+
       const namedFunctionExpression =
       function foo() {
         alert("namedFunctionExpression");
@@ -31,6 +33,7 @@
         }
       })();
 
+      /* exported init */
       function init() {
         const em = new Es6Method();
         const es6Method = document.getElementById("es6-method");
diff --git a/devtools/client/inspector/markup/test/doc_markup_events_04.html b/devtools/client/inspector/markup/test/doc_markup_events_04.html
index 81035e85d172..21ef59bc9ea8 100644
--- a/devtools/client/inspector/markup/test/doc_markup_events_04.html
+++ b/devtools/client/inspector/markup/test/doc_markup_events_04.html
@@ -16,15 +16,18 @@
     }
     </style>
     <script type="application/javascript">
+      "use strict";
+
       const constructedFunc = new Function();
 
       const constructedFuncWithBodyString =
         new Function('a', 'b', 'c', 'alert("constructedFuncWithBodyString");');
 
-      const multipleAssignment = foo = bar = function multi() {
+      const multipleAssignment = function multi() {
         alert("multipleAssignment");
       }
 
+      /* exported init */
       function init() {
         const constructedFunctionNode =
           document.getElementById("constructed-function");
@@ -81,10 +84,6 @@
           }
         }
       };
-
-      function* generator() {
-        alert("generator");
-      }
     </script>
   </head>
   <body onload="init();">
diff --git a/devtools/client/inspector/markup/test/doc_markup_events_jquery.html b/devtools/client/inspector/markup/test/doc_markup_events_jquery.html
index 7d4f134f52e3..fa3253f22353 100644
--- a/devtools/client/inspector/markup/test/doc_markup_events_jquery.html
+++ b/devtools/client/inspector/markup/test/doc_markup_events_jquery.html
@@ -16,6 +16,8 @@
     </style>
 
     <script type="application/javascript">
+      "use strict";
+
       const jq = document.location.search.substr(1);
 
       const script = document.createElement("script");
@@ -25,16 +27,16 @@
       document.head.appendChild(script);
 
       window.addEventListener("load", () => {
-        var handler1 = function liveDivDblClick() { alert(1); };
-        var handler2 = function liveDivDragStart() { alert(2); };
-        var handler3 = function liveDivDragLeave() { alert(3); };
-        var handler4 = function liveDivDragEnd() { alert(4); };
-        var handler5 = function liveDivDrop() { alert(5); };
-        var handler6 = function liveDivDragOver() { alert(6); };
-        var handler7 = function divClick1() { alert(7); };
-        var handler8 = function divClick2() { alert(8); };
-        var handler9 = function divKeyDown() { alert(9); };
-        var handler10 = function divDragOut() { alert(10); };
+        const handler1 = function liveDivDblClick() { alert(1); };
+        const handler2 = function liveDivDragStart() { alert(2); };
+        const handler3 = function liveDivDragLeave() { alert(3); };
+        const handler4 = function liveDivDragEnd() { alert(4); };
+        const handler5 = function liveDivDrop() { alert(5); };
+        const handler6 = function liveDivDragOver() { alert(6); };
+        const handler7 = function divClick1() { alert(7); };
+        const handler8 = function divClick2() { alert(8); };
+        const handler9 = function divKeyDown() { alert(9); };
+        const handler10 = function divDragOut() { alert(10); };
 
         if ($("#livediv").live) {
           $("#livediv").live( "dblclick", handler1);
@@ -52,7 +54,7 @@
           $(document).on( "dragout", "#livediv:xxxxx", handler10);
         }
 
-        var div = $("div")[0];
+        const div = $("div")[0];
         $(div).click(handler7);
         $(div).click(handler8);
         $(div).keydown(handler9);
diff --git a/devtools/client/inspector/markup/test/doc_markup_events_object_listener.html b/devtools/client/inspector/markup/test/doc_markup_events_object_listener.html
index b85c0c54c6ba..07000977bd24 100644
--- a/devtools/client/inspector/markup/test/doc_markup_events_object_listener.html
+++ b/devtools/client/inspector/markup/test/doc_markup_events_object_listener.html
@@ -8,6 +8,9 @@
       }
     </style>
     <script>
+      "use strict";
+
+      /* exported init */
       function init() {
         const valid = document.querySelector("#valid-object-listener");
         const validInvalid = document.querySelector("#valid-invalid-object-listeners");
diff --git a/devtools/client/inspector/markup/test/doc_markup_events_react_development_15.4.1.html b/devtools/client/inspector/markup/test/doc_markup_events_react_development_15.4.1.html
index 588833a85313..3ac39b83f9ab 100644
--- a/devtools/client/inspector/markup/test/doc_markup_events_react_development_15.4.1.html
+++ b/devtools/client/inspector/markup/test/doc_markup_events_react_development_15.4.1.html
@@ -22,7 +22,7 @@
           alert("inlineFunction");
         },
 
-        render: function () {
+        render() {
           return React.createElement(
             "div",
             null,
diff --git a/devtools/client/inspector/markup/test/doc_markup_events_react_development_15.4.1_jsx.html b/devtools/client/inspector/markup/test/doc_markup_events_react_development_15.4.1_jsx.html
index 1d6ad631edd7..5cab361d4a7f 100644
--- a/devtools/client/inspector/markup/test/doc_markup_events_react_development_15.4.1_jsx.html
+++ b/devtools/client/inspector/markup/test/doc_markup_events_react_development_15.4.1_jsx.html
@@ -24,7 +24,7 @@
           alert("inlineFunction");
         },
 
-        render: function () {
+        render() {
           return (
             <div>
               <h3 id="inlinejsx" onClick={this.inlineFunction}>Click for inlineFunction</h3>
diff --git a/devtools/client/inspector/markup/test/doc_markup_events_react_production_15.3.1.html b/devtools/client/inspector/markup/test/doc_markup_events_react_production_15.3.1.html
index ddb9a37dfd74..6f9f4c487871 100644
--- a/devtools/client/inspector/markup/test/doc_markup_events_react_production_15.3.1.html
+++ b/devtools/client/inspector/markup/test/doc_markup_events_react_production_15.3.1.html
@@ -22,7 +22,7 @@
           alert("inlineFunction");
         },
 
-        render: function () {
+        render() {
           return React.createElement(
             "div",
             null,
diff --git a/devtools/client/inspector/markup/test/doc_markup_events_react_production_15.3.1_jsx.html b/devtools/client/inspector/markup/test/doc_markup_events_react_production_15.3.1_jsx.html
index 1fe255955af3..f035caa9c840 100644
--- a/devtools/client/inspector/markup/test/doc_markup_events_react_production_15.3.1_jsx.html
+++ b/devtools/client/inspector/markup/test/doc_markup_events_react_production_15.3.1_jsx.html
@@ -24,7 +24,7 @@
           alert("inlineFunction");
         },
 
-        render: function () {
+        render() {
           return (
             <div>
               <h3 id="inlinejsx" onClick={this.inlineFunction}>Click for inlineFunction</h3>
diff --git a/devtools/client/performance/components/test/head.js b/devtools/client/performance/components/test/head.js
index 7540bfa4ade2..4b6627001ef9 100644
--- a/devtools/client/performance/components/test/head.js
+++ b/devtools/client/performance/components/test/head.js
@@ -19,6 +19,7 @@ let { require: browserRequire } = BrowserLoader({
   baseURI: "resource://devtools/client/performance/",
   window,
 });
+const DevToolsUtils = require("devtools/shared/DevToolsUtils");
 
 const $ = (selector, scope = document) => scope.querySelector(selector);
 const $$ = (selector, scope = document) => scope.querySelectorAll(selector);
diff --git a/devtools/client/performance/components/test/test_jit_optimizations_01.html b/devtools/client/performance/components/test/test_jit_optimizations_01.html
index 6759a75309df..cf2823d38783 100644
--- a/devtools/client/performance/components/test/test_jit_optimizations_01.html
+++ b/devtools/client/performance/components/test/test_jit_optimizations_01.html
@@ -13,15 +13,15 @@ Test the rendering of the JIT Optimizations tree. Tests when jit data has observ
 <pre id="test">
 <script src="head.js" type="application/javascript"></script>
 <script type="application/javascript">
+"use strict";
+
 window.onload = async function () {
   try {
     const ReactDOM = browserRequire("devtools/client/shared/vendor/react-dom");
     const React = browserRequire("devtools/client/shared/vendor/react");
     const JITOptimizations = React.createFactory(browserRequire("devtools/client/performance/components/JITOptimizations"));
     ok(JITOptimizations, "Should get JITOptimizations");
-    let opts;
-
-    opts = ReactDOM.render(JITOptimizations({
+    const opts = ReactDOM.render(JITOptimizations({
       onViewSourceInDebugger: function(){},
       frameData: {
         isMetaCategory: false,
diff --git a/devtools/server/tests/browser/storage-cookies-same-name.html b/devtools/server/tests/browser/storage-cookies-same-name.html
index 12157041c96e..235c8a451fcf 100644
--- a/devtools/server/tests/browser/storage-cookies-same-name.html
+++ b/devtools/server/tests/browser/storage-cookies-same-name.html
@@ -7,6 +7,7 @@
 <body onload="createCookies()">
 <script type="application/javascript">
 "use strict";
+// eslint-disable-next-line no-unused-vars
 function createCookies() {
   document.cookie = "name=value1;path=/;";
   document.cookie = "name=value2;path=/path2/;";
@@ -20,7 +21,7 @@ window.removeCookie = function (name) {
 window.clearCookies = function () {
   const cookies = document.cookie;
   for (const cookie of cookies.split(";")) {
-    removeCookie(cookie.split("=")[0]);
+    window.removeCookie(cookie.split("=")[0]);
   }
 };
 </script>
diff --git a/devtools/server/tests/browser/storage-dynamic-windows.html b/devtools/server/tests/browser/storage-dynamic-windows.html
index ce3daa33dd9e..22df8a255eb3 100644
--- a/devtools/server/tests/browser/storage-dynamic-windows.html
+++ b/devtools/server/tests/browser/storage-dynamic-windows.html
@@ -33,13 +33,13 @@ const idbGenerator = async function () {
   };
   const db = await new Promise(done => {
     request.onupgradeneeded = event => {
-      const db = event.target.result;
-      const store1 = db.createObjectStore("obj1", { keyPath: "id" });
+      const dbResult = event.target.result;
+      const store1 = dbResult.createObjectStore("obj1", { keyPath: "id" });
       store1.createIndex("name", "name", { unique: false });
       store1.createIndex("email", "email", { unique: true });
-      const store2 = db.createObjectStore("obj2", { keyPath: "id2" });
+      dbResult.createObjectStore("obj2", { keyPath: "id2" });
       store1.transaction.oncomplete = () => {
-        done(db);
+        done(dbResult);
       };
     };
   });
@@ -71,11 +71,11 @@ const idbGenerator = async function () {
   request = indexedDB.open("idb2", 1);
   const db2 = await new Promise(done => {
     request.onupgradeneeded = event => {
-      const db2 = event.target.result;
-      const store3 = db2.createObjectStore("obj3", { keyPath: "id3" });
+      const db2Result = event.target.result;
+      const store3 = db2Result.createObjectStore("obj3", { keyPath: "id3" });
       store3.createIndex("name2", "name2", { unique: true });
       store3.transaction.oncomplete = () => {
-        done(db2);
+        done(db2Result);
       }
     };
   });
diff --git a/devtools/server/tests/browser/storage-listings.html b/devtools/server/tests/browser/storage-listings.html
index 2755f2d4c297..98ac182bd0f1 100644
--- a/devtools/server/tests/browser/storage-listings.html
+++ b/devtools/server/tests/browser/storage-listings.html
@@ -35,13 +35,13 @@ const idbGenerator = async function () {
   };
   const db = await new Promise(done => {
     request.onupgradeneeded = event => {
-      const db = event.target.result;
-      const store1 = db.createObjectStore("obj1", { keyPath: "id" });
+      const dbResult = event.target.result;
+      const store1 = dbResult.createObjectStore("obj1", { keyPath: "id" });
       store1.createIndex("name", "name", { unique: false });
       store1.createIndex("email", "email", { unique: true });
-      const store2 = db.createObjectStore("obj2", { keyPath: "id2" });
+      dbResult.createObjectStore("obj2", { keyPath: "id2" });
       store1.transaction.oncomplete = () => {
-        done(db);
+        done(dbResult);
       };
     };
   });
@@ -73,11 +73,11 @@ const idbGenerator = async function () {
   request = indexedDB.open("idb2", 1);
   const db2 = await new Promise(done => {
     request.onupgradeneeded = event => {
-      const db2 = event.target.result;
-      const store3 = db2.createObjectStore("obj3", { keyPath: "id3" });
+      const db2Result = event.target.result;
+      const store3 = db2Result.createObjectStore("obj3", { keyPath: "id3" });
       store3.createIndex("name2", "name2", { unique: true });
       store3.transaction.oncomplete = () => {
-        done(db2);
+        done(db2Result);
       }
     };
   });
diff --git a/devtools/server/tests/browser/storage-secured-iframe.html b/devtools/server/tests/browser/storage-secured-iframe.html
index 4d5e021c9aab..c2fe4ed485ec 100644
--- a/devtools/server/tests/browser/storage-secured-iframe.html
+++ b/devtools/server/tests/browser/storage-secured-iframe.html
@@ -8,7 +8,7 @@ Iframe for testing multiple host detetion in storage actor
 </head>
 <body>
 <script type="application/javascript">
-
+"use strict";
 document.cookie = "sc1=foobar;";
 localStorage.setItem("iframe-s-ls1", "foobar");
 sessionStorage.setItem("iframe-s-ss1", "foobar-2");
@@ -20,10 +20,10 @@ const idbGenerator = async function () {
   };
   const db = await new Promise(done => {
     request.onupgradeneeded = event => {
-      const db = event.target.result;
-      const store1 = db.createObjectStore("obj-s1", { keyPath: "id" });
+      const dbResult = event.target.result;
+      const store1 = dbResult.createObjectStore("obj-s1", { keyPath: "id" });
       store1.transaction.oncomplete = () => {
-        done(db);
+        done(dbResult);
       };
     };
   });
@@ -44,12 +44,12 @@ const idbGenerator = async function () {
   request = indexedDB.open("idb-s2", 1);
   const db2 = await new Promise(done => {
     request.onupgradeneeded = event => {
-      const db2 = event.target.result;
+      const db2Result = event.target.result;
       const store3 =
-        db2.createObjectStore("obj-s2", { keyPath: "id3", autoIncrement: true });
+        db2Result.createObjectStore("obj-s2", { keyPath: "id3", autoIncrement: true });
       store3.createIndex("name2", "name2", { unique: true });
       store3.transaction.oncomplete = () => {
-        done(db2);
+        done(db2Result);
       };
     };
   });
diff --git a/devtools/server/tests/browser/storage-updates.html b/devtools/server/tests/browser/storage-updates.html
index bcdafd465e87..594c28ce0ff5 100644
--- a/devtools/server/tests/browser/storage-updates.html
+++ b/devtools/server/tests/browser/storage-updates.html
@@ -39,7 +39,7 @@ window.clearLocalAndSessionStores = function() {
 window.clearCookies = function() {
   const cookies = document.cookie;
   for (const cookie of cookies.split(";")) {
-    removeCookie(cookie.split("=")[0]);
+    window.removeCookie(cookie.split("=")[0]);
   }
 };
 </script>
diff --git a/devtools/server/tests/browser/stylesheets-nested-iframes.html b/devtools/server/tests/browser/stylesheets-nested-iframes.html
index 9ffec13c7fa0..eb6c3718677b 100644
--- a/devtools/server/tests/browser/stylesheets-nested-iframes.html
+++ b/devtools/server/tests/browser/stylesheets-nested-iframes.html
@@ -13,8 +13,10 @@
   <p>A test page with nested iframes</p>
   <iframe></iframe>
   <script type="application/javascript">
+    "use strict";
+
     const iframe = document.querySelector("iframe");
-    let i = parseInt(location.href.split("?")[1]) || 1;
+    let i = parseInt(location.href.split("?")[1], 10) || 1;
 
     // The frame can't have the same src URL as any of its ancestors.
     // This will not infinitely recurse because a frame won't get a content