Bug 1788037 - Turn on ESLint rule for prefer-boolean-length-check for dom. r=asuth,karlt

Differential Revision: https://phabricator.services.mozilla.com/D155965

.eslintrc.js

@@ -477,7 +477,7 @@ module.exports = {
       },
     },
     {
-      files: ["dom/**", "netwerk/**"],
+      files: ["netwerk/**"],
       rules: {
         "mozilla/prefer-boolean-length-check": "off",
       },

dom/animation/test/mozilla/file_restyles.html

@@ -410,7 +410,7 @@ waitForAllPaints(() => {
         now = document.timeline.currentTime;
         elapsed = (now - timeAtStart);
         markers = await observeStyling(1);
-        if (markers.length > 0) {
+        if (markers.length) {
           break;
         }
       }
@@ -437,7 +437,7 @@ waitForAllPaints(() => {
       else if (elapsed.toPrecision(10) > 200)
         expectedMarkersLengthValid = markers.length == 1;
       else
-        expectedMarkersLengthValid = markers.length == 0;
+        expectedMarkersLengthValid = !markers.length;
       ok(expectedMarkersLengthValid,
          'Transform animation running on the element which is scrolled out ' +
          'should be unthrottled after around 200ms have elapsed. now: ' +
@@ -472,7 +472,7 @@ waitForAllPaints(() => {
         now = document.timeline.currentTime;
         elapsed = (now - timeAtStart);
         markers = await observeStyling(1);
-        if (markers.length > 0) {
+        if (markers.length) {
           break;
         }
       }
@@ -495,7 +495,7 @@ waitForAllPaints(() => {
       else if (elapsed.toPrecision(10) > 200)
         expectedMarkersLengthValid = markers.length == 1;
       else
-        expectedMarkersLengthValid = markers.length == 0;
+        expectedMarkersLengthValid = !markers.length;
       ok(expectedMarkersLengthValid,
          'Transform animation running on out of view element ' +
          'should be unthrottled after around 200ms have elapsed. now: ' +

dom/base/test/chrome/file_bug990812-1.xhtml

@@ -39,7 +39,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=990812
         var next = order.shift();
         window.arguments[0].is(msg.data, next, "received test:" + next);
 
-        if (order.length == 0) {
+        if (!order.length) {
           window.arguments[0].setTimeout(function() { this.next(); });
           window.close();
         }

dom/base/test/chrome/file_bug990812-3.xhtml

@@ -28,7 +28,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=990812
         mm.addMessageListener("test", function onMessage(msg) {
           is(msg.data, order.shift(), "correct message " + msg.data);
 
-          if (order.length == 0) {
+          if (!order.length) {
             mm.removeMessageListener("test", onMessage);
             resolve();
           }

dom/base/test/chrome/file_bug990812.xhtml

@@ -33,7 +33,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=990812
         var next = order.shift();
         opener.wrappedJSObject.is(msg.data, next, "received test:" + next);
 
-        if (order.length == 0) {
+        if (!order.length) {
           opener.setTimeout("next()");
           window.close();
         }

dom/base/test/chrome/test_bug1346936.html

@@ -43,7 +43,7 @@ window.onload = function() {
             var scripts = dbg.findScripts({
                 url: "http://mochi.test:8888/tests/dom/base/test/chrome/nochrome_bug1346936.js",
             });
-            ok(scripts.length > 0, "Should be able to find script");
+            ok(scripts.length, "Should be able to find script");
 
             is(scripts[0].source.sourceMapURL, "foo.js.map");
             SimpleTest.finish();

dom/base/test/chrome/test_bug765993.html

@@ -43,7 +43,7 @@ window.onload = function() {
             var scripts = dbg.findScripts({
                 url: "http://mochi.test:8888/tests/dom/base/test/chrome/nochrome_bug765993.js",
             });
-            ok(scripts.length > 0, "Should be able to find script");
+            ok(scripts.length, "Should be able to find script");
 
             is(scripts[0].source.sourceMapURL, "foo.js.map");
             SimpleTest.finish();

dom/base/test/chrome/test_bug884693.xhtml

@@ -41,7 +41,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=884693
               msg.category.includes("chrome javascript") &&
               msg.message.includes("Unknown event")));
 
-          if (messages.length > 0) {
+          if (messages.length) {
             info(`Got console messages ${messages}`);
           }
           is(messages.length, expectedMessages.length, "Got expected message count");

dom/base/test/chrome/test_bug990812.xhtml

@@ -28,7 +28,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=990812
   ];
 
   function next() {
-    if (tests.length > 0) {
+    if (tests.length) {
       var file = tests.shift();
       info("-- running " + file);
       window.openDialog(file, "_blank", "chrome,noopener", window);

dom/base/test/chrome/window_nsITextInputProcessor.xhtml

@@ -4134,7 +4134,7 @@ async function runCallbackTests(aForTests)
   function waitUntilNotificationsReceived()
   {
     return new Promise(resolve => {
-      if (notifications.length > 0) {
+      if (notifications.length) {
         SimpleTest.executeSoon(resolve);
       } else {
         waitingNextNotification = resolve;
@@ -4167,8 +4167,8 @@ async function runCallbackTests(aForTests)
       is(aNotification.reversed, aExpected.reversed || false,
         `${aDescription} should cause selection change notification whose reversed is ${aExpected.reversed || false}`);
     }
-    is(aNotification.collapsed, aExpected.hasRange === false || aExpected.text.length == 0,
+    is(aNotification.collapsed, aExpected.hasRange === false || !aExpected.text.length,
-      `${aDescription} should cause selection change notification whose collapsed is ${aExpected.hasRange === false || aExpected.text.length == 0}`);
+      `${aDescription} should cause selection change notification whose collapsed is ${aExpected.hasRange === false || !aExpected.text.length}`);
     is(aNotification.writingMode, aExpected.writingMode || "horizontal-tb",
       `${aDescription} should cause selection change notification whose writingMode is ${aExpected.writingMode || "horizontal-tb"}`);
     is(aNotification.causedByComposition, aExpected.causedByComposition || false,
@@ -4391,7 +4391,7 @@ async function runFocusNotificationTestAfterDrop() {
     notifications.length > 1,
     "runFocusNotificationTestAfterDrop: At least two notifications should be fired"
   );
-  if (notifications.length > 0) {
+  if (notifications.length) {
     is(
       notifications[notifications.length - 1],
       "notify-focus",

dom/base/test/delayedServerEvents.sjs

@@ -16,7 +16,7 @@ var strings_to_send = [
 var resp = null;
 
 function sendNextString() {
-  if (strings_to_send.length == 0) {
+  if (!strings_to_send.length) {
     timer.cancel();
     resp.finish();
     timer = null;

dom/base/test/file_bug416317.xhtml

@@ -437,7 +437,7 @@
           try {
             var single = root.querySelector(query);
 
-            var pass = found.length == 0 && single === null ||
+            var pass = !found.length && single === null ||
               found.length && found[0] == single;
 
             assert(expect, type + ".querySelector: " + query);

dom/base/test/test_bug218236.html

@@ -62,7 +62,7 @@ function doAbort2() {
 /* Utility functions */
 
 function runNextTest() {
-  if (tests.length > 0) {
+  if (tests.length) {
     var test = tests.shift();
 
     // Initialize state variables

dom/base/test/test_bug466080.html

@@ -103,7 +103,7 @@ async function onWindowLoad() {
     async function runTest(test) {
         if (test.cleanEnableCertOnPreflight) {
             await SpecialPowers.pushPrefEnv({"set": [["network.cors_preflight.allow_client_cert", false]]});
-            if (alltests.length == 0) {
+            if (!alltests.length) {
                 SimpleTest.finish();
             } else {
                 runTest(alltests.shift());
@@ -131,7 +131,7 @@ async function onWindowLoad() {
                 var success = eval(xhr.status + test.status_check);
                 ok(success, test.error);
 
-                if (alltests.length == 0) {
+                if (!alltests.length) {
                     SimpleTest.finish();
                 } else {
                     runTest(alltests.shift());

dom/base/test/test_bug475156.html

@@ -285,7 +285,7 @@ function drive(test)
       }
       if (this.readyState == 4) {
         test.done(this);
-        if (tests.length == 0)
+        if (!tests.length)
           SimpleTest.finish();
         else
           drive(tests.shift());

dom/base/test/test_bug782342.html

@@ -45,9 +45,9 @@ function checkHeaders(xhrInner) {
   ok(contentType == true, "Content-type is part of the headers!");
 
   var ct = xhrInner.getResponseHeader('content-type');
-  ok(ct.length > 0, 'Get Response Header - content type: ' + ct);
+  ok(ct.length, 'Get Response Header - content type: ' + ct);
   var cl = xhrInner.getResponseHeader('content-length');
-  ok(cl.length > 0, 'Get Response Header - content length: ' + cl);
+  ok(cl.length, 'Get Response Header - content length: ' + cl);
 }
 
 xhr.addEventListener("load", function () {

dom/base/test/test_content_iterator_post_order.html

@@ -456,7 +456,7 @@ SimpleTest.waitForFocus(function () {
    * Basic tests with complicated tree.
    */
   function check(aIter, aExpectedResult, aDescription) {
-    if (aExpectedResult.length > 0) {
+    if (aExpectedResult.length) {
       is(SpecialPowers.unwrap(aIter.currentNode), aExpectedResult[0],
         `${aDescription}: currentNode should be the text node immediately after initialization (got: ${getNodeDescription(aIter.currentNode)}, expected: ${getNodeDescription(aExpectedResult[0])})`);
       ok(!aIter.isDone, `${aDescription}: isDone shouldn't be true immediately after initialization`);

dom/base/test/test_content_iterator_pre_order.html

@@ -456,7 +456,7 @@ SimpleTest.waitForFocus(function () {
    * Basic tests with complicated tree.
    */
   function check(aIter, aExpectedResult, aDescription) {
-    if (aExpectedResult.length > 0) {
+    if (aExpectedResult.length) {
       is(SpecialPowers.unwrap(aIter.currentNode), aExpectedResult[0],
         `${aDescription}: currentNode should be the text node immediately after initialization (got: ${getNodeDescription(aIter.currentNode)}, expected: ${getNodeDescription(aExpectedResult[0])})`);
       ok(!aIter.isDone, `${aDescription}: isDone shouldn't be true immediately after initialization`);

dom/base/test/test_content_iterator_subtree.html

@@ -381,7 +381,7 @@ SimpleTest.waitForFocus(function () {
    * Basic tests with complicated tree.
    */
   function check(aIter, aExpectedResult, aDescription) {
-    if (aExpectedResult.length > 0) {
+    if (aExpectedResult.length) {
       is(SpecialPowers.unwrap(aIter.currentNode), aExpectedResult[0],
         `${aDescription}: currentNode should be the text node immediately after initialization (got: ${getNodeDescription(aIter.currentNode)}, expected: ${getNodeDescription(aExpectedResult[0])})`);
       ok(!aIter.isDone, `${aDescription}: isDone shouldn't be true immediately after initialization`);

dom/base/test/test_navigator_language.html

@@ -131,7 +131,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=889335
 
         is(navigator.language, data.language);
         is(navigator.languages.length, data.languages.length);
-        if (navigator.languages.length > 0) {
+        if (navigator.languages.length) {
           is(navigator.languages[0], navigator.language)
         }
         for (var j = 0; j < navigator.languages.length; ++j) {

dom/base/test/unit/test_range.js

@@ -45,7 +45,7 @@ const parser = getParser();
  */
 function evalXPathInDocumentFragment(aContextNode, aPath) {
   Assert.equal(ChromeUtils.getClassName(aContextNode), "DocumentFragment");
-  Assert.ok(aContextNode.childNodes.length > 0);
+  Assert.ok(aContextNode.childNodes.length);
   if (aPath == ".") {
     return aContextNode;
   }

dom/bindings/test/test_jsimplemented_eventhandler.html

@@ -16,7 +16,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=1186696
   function doTest() {
     var values = [ function() {}, 5, null, undefined, "some string", {} ];
 
-    while (values.length != 0) {
+    while (values.length) {
       var value = values.pop();
       var t = new TestInterfaceJS();
       t.onsomething = value;

dom/cache/test/xpcshell/test_migration.js

@@ -14,7 +14,7 @@ add_task(async function testSteps() {
 
   const requestList = await cache.keys();
 
-  ok(requestList.length > 0, "should have at least one request in cache");
+  ok(requestList.length, "should have at least one request in cache");
   for (const request of requestList) {
     ok(request, "each request in list should be non-null");
     ok(
@@ -41,7 +41,7 @@ add_task(async function testSteps() {
     })
   );
 
-  ok(responseList.length > 0, "should have at least one response in cache");
+  ok(responseList.length, "should have at least one response in cache");
   for (const response of responseList) {
     ok(response, "each response should be non-null");
     // reponse.url is a empty string in current test file. It should test for

dom/canvas/test/test_imagebitmap.html

@@ -152,7 +152,7 @@ function testExceptions() {
         tempWorker.postMessage(imageData.data.buffer, [imageData.data.buffer]);
         tempWorker.terminate();
 
-        ok(imageData.data.length == 0, "Get a neutured ImageData.");
+        ok(!imageData.data.length, "Get a neutured ImageData.");
         resolve(createImageBitmap(imageData));
       }
     });

dom/canvas/test/test_invalid_mime_type_blob.html

@@ -68,7 +68,7 @@ let tests = [
 ];
 
 function next() {
-  if (tests.length == 0) {
+  if (!tests.length) {
     SimpleTest.finish();
     return;
   }

dom/crypto/test/test_WebCrypto_ECDH.html

@@ -35,7 +35,7 @@ TestArray.addTest(
                (x.publicKey.algorithm.namedCurve == alg.namedCurve) &&
                (x.publicKey.type == "public") &&
                x.publicKey.extractable &&
-               (x.publicKey.usages.length == 0) &&
+               (!x.publicKey.usages.length) &&
                exists(x.privateKey) &&
                (x.privateKey.algorithm.name == alg.name) &&
                (x.privateKey.algorithm.namedCurve == alg.namedCurve) &&

dom/events/test/pointerevents/test_bug1403055.html

@@ -43,8 +43,8 @@ function withoutImplicitlyPointerCaptureForTouch() {
   });
 
   done.addEventListener("mouseup", () => {
-    ok(target0_events.length == 0, " should receive " + target0_events + " on target0");
+    ok(!target0_events.length, " should receive " + target0_events + " on target0");
-    ok(target1_events.length == 0, " should receive " + target1_events + " on target1");
+    ok(!target1_events.length, " should receive " + target1_events + " on target1");
     SpecialPowers.pushPrefEnv({"set": [["dom.w3c_pointer_events.implicit_capture", true]]},
                               withImplicitlyPointerCaptureForTouch);
   }, {once : true});
@@ -68,7 +68,7 @@ function withImplicitlyPointerCaptureForTouch() {
   });
 
   done.addEventListener("mouseup", () => {
-    ok(target0_events.length == 0, " should receive " + target0_events + " on target0");
+    ok(!target0_events.length, " should receive " + target0_events + " on target0");
     SimpleTest.finish();
   }, {once : true});
 

dom/events/test/pointerevents/test_bug1420589_1.html

@@ -63,7 +63,7 @@ function withoutImplicitlyPointerCaptureForTouch() {
     ok(expectedEvents.includes(e.data), " don't expect " + e.data);
     expectedEvents = expectedEvents.filter(item => item !== e.data);
     if (e.data == "iframe2 touchend") {
-      ok(expectedEvents.length == 0, " expect " + expectedEvents);
+      ok(!expectedEvents.length, " expect " + expectedEvents);
       SimpleTest.finish();
     }
   })

dom/events/test/pointerevents/test_bug1420589_2.html

@@ -66,7 +66,7 @@ function withoutImplicitlyPointerCaptureForTouch() {
     ok(expectedEvents.includes(e.data), " don't expect " + e.data);
     expectedEvents = expectedEvents.filter(item => item !== e.data);
     if (e.data == "div1 touchend") {
-      ok(expectedEvents.length == 0, " expect " + expectedEvents);
+      ok(!expectedEvents.length, " expect " + expectedEvents);
       SimpleTest.finish();
     }
   })

dom/events/test/pointerevents/test_bug1420589_3.html

@@ -59,7 +59,7 @@ function withoutImplicitlyPointerCaptureForTouch() {
     ok(expectedEvents.includes(e.data), " don't expect " + e.data);
     expectedEvents = expectedEvents.filter(item => item !== e.data);
     if (e.data == "iframe1 touchend") {
-      ok(expectedEvents.length == 0, " expect " + expectedEvents);
+      ok(!expectedEvents.length, " expect " + expectedEvents);
       SimpleTest.finish();
     }
   })

dom/events/test/pointerevents/test_remove_frame_when_got_pointer_capture.html

@@ -72,7 +72,7 @@ function startTest() {
   synthesizeMouseAtCenter(div2, {type: "mousemove"}, iframe.contentWindow);
   synthesizeMouseAtCenter(div2, {type: "mouseup"}, iframe.contentWindow);
 
-  ok(divEvents.length == 0, " expect " + divEvents);
+  ok(!divEvents.length, " expect " + divEvents);
 
   divEvents = [
     "pointerdown",
@@ -113,7 +113,7 @@ function startTest() {
   synthesizeTouch(div2, 5, 5, { type: "touchmove" }, iframe.contentWindow);
   synthesizeTouch(div2, 5, 5, { type: "touchend" }, iframe.contentWindow);
 
-  ok(divEvents.length == 0, " expect " + divEvents);
+  ok(!divEvents.length, " expect " + divEvents);
 
   divEvents = [
     "pointerdown",
@@ -154,7 +154,7 @@ function startTest() {
   synthesizeTouch(div2, 5, 5, { type: "touchmove" }, iframe.contentWindow);
   synthesizeTouch(div2, 5, 5, { type: "touchcancel" }, iframe.contentWindow);
 
-  ok(divEvents.length == 0, " expect " + divEvents);
+  ok(!divEvents.length, " expect " + divEvents);
 
   SimpleTest.finish();
 }

dom/events/test/test_bug409604.html

@@ -130,7 +130,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=409604
       var accessChar = String.fromCharCode(code).toUpperCase();
       pressAccessKey({key: accessChar});
     }
-    ok(focusArray.length == 0, "(focus) unhandled elements remaining: " + focusArray.join(","));
+    ok(!focusArray.length, "(focus) unhandled elements remaining: " + focusArray.join(","));
   }
 
   function createUnfocusableElement(elem, accesskey) {

dom/events/test/test_bug422132.html

@@ -107,7 +107,7 @@ function runTests()
       if (test.check) {
         test.check();
       }
-      if (tests.length == 0) {
+      if (!tests.length) {
         SimpleTest.finish();
         return;
       }

dom/events/test/test_dragstart.html

@@ -560,7 +560,7 @@ function doDragOverSynthetic(event)
 function onDragStartDraggable(event)
 {
   var dt = event.dataTransfer;
-  ok(SpecialPowers.wrap(dt).mozItemCount == 0 && dt.types.length == 0 && event.originalTarget == gDragInfo.target, gDragInfo.testid);
+  ok(SpecialPowers.wrap(dt).mozItemCount == 0 && !dt.types.length && event.originalTarget == gDragInfo.target, gDragInfo.testid);
 
   event.preventDefault();
   gExtraDragTests++;

dom/events/test/test_event_handler_cc.html

@@ -17,7 +17,7 @@
     }
 
     function weak_ref_dead(r) {
-      return SpecialPowers.nondeterministicGetWeakMapKeys(r).length == 0;
+      return !SpecialPowers.nondeterministicGetWeakMapKeys(r).length;
     }
 
     function setupTarget1() {

dom/events/test/test_mouse_enterleave_iframe.html

@@ -125,7 +125,7 @@ function waitForEnterLeaveEvents(aEnterTarget, aLeaveTarget) {
         return;
       }
 
-      if (expectedEvents.length == 0) {
+      if (!expectedEvents.length) {
         // Trigger a reflow which will generate synthesized mouse move event.
         reflow();
         // Now wait a bit to see if there is any unexpected event fired.

dom/events/test/test_paste_image.html

@@ -118,7 +118,7 @@
        "Getting @items twice should return the same object");
     var haveFiles = false;
     ok(items instanceof DataTransferItemList, "@items implements DataTransferItemList");
-    ok(items.length > 0, "@items is not empty");
+    ok(items.length, "@items is not empty");
     for (var i = 0; i < items.length; i++) {
       var item = items[i];
       ok(item instanceof DataTransferItem, "each element of @items must implement DataTransferItem");
@@ -136,7 +136,7 @@
 
     is(files, e.clipboardData.files,
        "Getting the files array twice should return the same array");
-    ok(files.length > 0, "There should be at least one file in the clipboard");
+    ok(files.length, "There should be at least one file in the clipboard");
     for (var i = 0; i < files.length; i++) {
       var file = files[i];
       ok(file instanceof File, ".files should contain only File objects");

dom/file/tests/common_blob.js

@@ -206,7 +206,7 @@ function testSlice(file, size, type, contents, fileType, range) {
   }
 
   function runNextTest() {
-    if (indexes.length == 0) {
+    if (!indexes.length) {
       return Promise.resolve(true);
     }
 

dom/file/tests/test_blobconstructor.html

@@ -200,8 +200,8 @@ let currentTest = null;
 let testCounter = 0;
 
 function runTests() {
-  if (!currentTest || currentTest[2].length == 0) {
+  if (!currentTest || !currentTest[2].length) {
-    if (testData.length == 0) {
+    if (!testData.length) {
       SimpleTest.finish();
       return;
     }

dom/grid/test/chrome/test_grid_object.html

@@ -54,7 +54,7 @@ function runTests() {
     );
 
     // test that the grid has cols and rows properties
-    if (gridFragments.length > 0) {
+    if (gridFragments.length) {
       let grid = gridFragments[0];
       isnot(typeof(grid.cols), "undefined", id + ": Grid.cols property exists.");
       isnot(typeof(grid.rows), "undefined", id + ": Grid.rows property exists.");

dom/html/test/file_fullscreen-featurePolicy.html

@@ -39,7 +39,7 @@ var tests = [
 ];
 
 async function nextTest() {
-  if (tests.length == 0) {
+  if (!tests.length) {
     opener.nextTest();
     return;
   }

dom/html/test/file_fullscreen-top-layer.html

@@ -149,7 +149,7 @@ function secondClick(evt) {
 }
 
 function exitFullscreen() {
-  if (tests.length > 0) {
+  if (tests.length) {
     nextTest();
   } else {
     opener.nextTest();

dom/html/test/forms/test_MozEditableElement_setUserInput.html

@@ -172,13 +172,13 @@ SimpleTest.waitForFocus(async () => {
            `Only one "input" event should be dispatched when setUserInput("${test.input.before}") is called before ${tag} gets focus`);
       }
     }
-    if (inputEvents.length > 0) {
+    if (inputEvents.length) {
       if (SpecialPowers.wrap(target).isInputEventTarget) {
         if (test.type === "time") {
           todo(inputEvents[0] instanceof InputEvent,
                `"input" event should be dispatched with InputEvent interface when setUserInput("${test.input.before}") is called before ${tag} gets focus`);
         } else {
-          if (beforeInputEvents.length > 0 && test.result.fireBeforeInputEvent) {
+          if (beforeInputEvents.length && test.result.fireBeforeInputEvent) {
             is(beforeInputEvents[0].cancelable, kSetUserInputCancelable,
                `"beforeinput" event for "insertReplacementText" should be cancelable when setUserInput("${test.input.before}") is called before ${tag} gets focus unless it's suppressed by the pref`);
             is(beforeInputEvents[0].inputType, "insertReplacementText",
@@ -258,13 +258,13 @@ SimpleTest.waitForFocus(async () => {
            `Only one "input" event should be dispatched when setUserInput("${test.input.after}") is called after ${tag} gets focus`);
       }
     }
-    if (inputEvents.length > 0) {
+    if (inputEvents.length) {
       if (SpecialPowers.wrap(target).isInputEventTarget) {
         if (test.type === "time") {
           todo(inputEvents[0] instanceof InputEvent,
                `"input" event should be dispatched with InputEvent interface when setUserInput("${test.input.after}") is called after ${tag} gets focus`);
         } else {
-          if (beforeInputEvents.length > 0 && test.result.fireBeforeInputEvent) {
+          if (beforeInputEvents.length && test.result.fireBeforeInputEvent) {
             is(beforeInputEvents[0].cancelable, kSetUserInputCancelable,
                `"beforeinput" event should be cancelable when setUserInput("${test.input.after}") is called after ${tag} gets focus unless it's suppressed by the pref`);
             is(beforeInputEvents[0].inputType, "insertReplacementText",
@@ -407,12 +407,12 @@ SimpleTest.waitForFocus(async () => {
     reset();
     SpecialPowers.wrap(target).setUserInput(aValidValue);
     is(beforeInputEvents.length, 1, `Calling  ${tag}.setUserInput(${aValidValue}) should cause a "beforeinput" event (before gets focus)`);
-    if (beforeInputEvents.length > 0) {
+    if (beforeInputEvents.length) {
       is(beforeInputEvents[0].validity, false,
          `The ${tag} should be invalid at "beforeinput" event (before gets focus)`);
     }
     is(inputEvents.length, 1, `Calling  ${tag}.setUserInput(${aValidValue}) should cause a "input" event (before gets focus)`);
-    if (inputEvents.length > 0) {
+    if (inputEvents.length) {
       is(inputEvents[0].validity, true,
          `The ${tag} should be valid at "input" event (before gets focus)`);
     }
@@ -433,12 +433,12 @@ SimpleTest.waitForFocus(async () => {
     reset();
     SpecialPowers.wrap(target).setUserInput(aValidValue);
     is(beforeInputEvents.length, 1, `Calling  ${tag}.setUserInput(${aValidValue}) should cause a "beforeinput" event (after gets focus)`);
-    if (beforeInputEvents.length > 0) {
+    if (beforeInputEvents.length) {
       is(beforeInputEvents[0].validity, false,
          `The ${tag} should be invalid at "beforeinput" event (after gets focus)`);
     }
     is(inputEvents.length, 1, `Calling  ${tag}.setUserInput(${aValidValue}) should cause a "input" event (after gets focus)`);
-    if (inputEvents.length > 0) {
+    if (inputEvents.length) {
       is(inputEvents[0].validity, true,
          `The ${tag} should be valid at "input" event (after gets focus)`);
     }

dom/html/test/forms/test_input_color_picker_popup.html

@@ -58,7 +58,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=885996
       return "";
     };
 
-    while (testData.length != 0) {
+    while (testData.length) {
       currentTest = testData.shift();
       element = document.getElementById(currentTest.id);
 

dom/html/test/forms/test_input_setting_value.html

@@ -471,7 +471,7 @@ SimpleTest.waitForFocus(() => {
       is(input.value, "hig",
          `${description}The value should be set to the specified value in "beforeinput" event listener since the event target was already modified`);
       is(inputEvents.length, 1, `${description}"input" event should be fired`);
-      if (inputEvents.length > 0) {
+      if (inputEvents.length) {
         is(inputEvents[0].inputType,
            "insertReplacementText", `${description}inputType of "input" event should be "insertReplacementText"`);
         is(inputEvents[0].data, "def",
@@ -550,7 +550,7 @@ SimpleTest.waitForFocus(() => {
       // Different from Chrome
       is(inputEvents.length, 1,
          `${description}"input" event should be fired even if the frame of target is destroyed`);
-      if (inputEvents.length > 0) {
+      if (inputEvents.length) {
         is(inputEvents[0].inputType,
            "insertReplacementText", `${description}inputType of "input" event should be "insertReplacementText"`);
         is(inputEvents[0].data, "def",
@@ -597,7 +597,7 @@ SimpleTest.waitForFocus(() => {
       is(input.value, "hig",
          `${description}The value should be set to the specified value in "beforeinput" event listener since the event target was already modified`);
       is(inputEvents.length, 1, `${description}"input" event should be fired`);
-      if (inputEvents.length > 0) {
+      if (inputEvents.length) {
         is(inputEvents[0].inputType,
            "insertReplacementText", `${description}inputType of "input" event should be "insertReplacementText"`);
         is(inputEvents[0].data, "def",

dom/html/test/reflect.js

@@ -596,7 +596,7 @@ function reflectLimitedEnumerated(aParameters) {
       null,
       "Missing default value should be null for nullable attributes"
     );
-    ok(validValues.length > 0, "We better have at least one valid value");
+    ok(validValues.length, "We better have at least one valid value");
     element.setAttribute(contentAttr, validValues[0]);
     ok(
       element.hasAttribute(contentAttr),

dom/html/test/test_bug428135.xhtml

@@ -66,12 +66,12 @@ function testSubmitResetEvents() {
 
   expectedCurrentTargets = new Array(document, outerForm, outerForm, document);
   outerSubmit.click();
-  ok(expectedCurrentTargets.length == 0,
+  ok(!expectedCurrentTargets.length,
      "(1) expectedCurrentTargets isn't empty!");
 
   expectedCurrentTargets = new Array(document, outerForm, outerForm, document);
   outerReset.click();
-  ok(expectedCurrentTargets.length == 0,
+  ok(!expectedCurrentTargets.length,
      "(2) expectedCurrentTargets isn't empty!");
 
   // Because of bug 428135, submit shouldn't propagate
@@ -79,7 +79,7 @@ function testSubmitResetEvents() {
   expectedCurrentTargets = 
     new Array(document, outerForm, outerSubmitDispatcher, outerSubmitDispatcher);
   outerSubmitDispatcher.click();
-  ok(expectedCurrentTargets.length == 0,
+  ok(!expectedCurrentTargets.length,
      "(3) expectedCurrentTargets isn't empty!");
 
   // Because of bug 428135, reset shouldn't propagate
@@ -87,7 +87,7 @@ function testSubmitResetEvents() {
   expectedCurrentTargets =
     new Array(document, outerForm, outerResetDispatcher, outerResetDispatcher);
   outerResetDispatcher.click();
-  ok(expectedCurrentTargets.length == 0,
+  ok(!expectedCurrentTargets.length,
      "(4) expectedCurrentTargets isn't empty!");
 
   // Because of bug 428135, submit shouldn't propagate
@@ -95,7 +95,7 @@ function testSubmitResetEvents() {
   expectedCurrentTargets = 
     new Array(document, outerForm, outerChild, innerForm, innerForm, outerChild);
   innerSubmit.click();
-  ok(expectedCurrentTargets.length == 0,
+  ok(!expectedCurrentTargets.length,
      "(5) expectedCurrentTargets isn't empty!");
 
   // Because of bug 428135, reset shouldn't propagate
@@ -103,7 +103,7 @@ function testSubmitResetEvents() {
   expectedCurrentTargets = 
     new Array(document, outerForm, outerChild, innerForm, innerForm, outerChild);
   innerReset.click();
-  ok(expectedCurrentTargets.length == 0,
+  ok(!expectedCurrentTargets.length,
      "(6) expectedCurrentTargets isn't empty!");
 
   // Because of bug 428135, submit shouldn't propagate
@@ -112,7 +112,7 @@ function testSubmitResetEvents() {
     new Array(document, outerForm, outerChild, innerForm, innerSubmitDispatcher,
               innerSubmitDispatcher);
   innerSubmitDispatcher.click();
-  ok(expectedCurrentTargets.length == 0,
+  ok(!expectedCurrentTargets.length,
      "(7) expectedCurrentTargets isn't empty!");
 
   // Because of bug 428135, reset shouldn't propagate
@@ -121,7 +121,7 @@ function testSubmitResetEvents() {
     new Array(document, outerForm, outerChild, innerForm, innerResetDispatcher,
               innerResetDispatcher);
   innerResetDispatcher.click();
-  ok(expectedCurrentTargets.length == 0,
+  ok(!expectedCurrentTargets.length,
      "(8) expectedCurrentTargets isn't empty!");
 }
 

dom/html/test/test_document-element-inserted.html

@@ -34,7 +34,7 @@ var tests = [
 ]
 
 function next() {
-    if (tests.length > 0) {
+    if (tests.length) {
         var t = tests.shift();
         loc = t.substring(t.indexOf("test"));
         media.setAttribute("src",t);

dom/html/test/test_external_protocol_iframe.html

@@ -60,7 +60,7 @@ let tests = [
 ];
 
 function next() {
-  if (tests.length == 0) {
+  if (!tests.length) {
     SimpleTest.finish();
     return;
   }

dom/html/test/test_frame_count_with_synthetic_doc.html

@@ -9,7 +9,7 @@
     SimpleTest.waitForExplicitFinish();
     function getWindowLength() {
       setTimeout(function() {
-        if (window.length > 0) {
+        if (window.length) {
           ok(false, "Synthetic document shouldn't be exposed");
         }
 

dom/html/test/test_window_open_close.html

@@ -38,7 +38,7 @@ function popupLoad(win)
 
 function next()
 {
-  if (TESTS.length == 0) {
+  if (!TESTS.length) {
     SimpleTest.finish();
   } else {
     var test = TESTS.shift();

dom/indexedDB/test/head.js

@@ -56,7 +56,7 @@ function unregisterAllPopupEventHandlers(win) {
 function triggerMainCommand(popup) {
   info("triggering main command");
   let notifications = popup.childNodes;
-  ok(notifications.length > 0, "at least one notification displayed");
+  ok(notifications.length, "at least one notification displayed");
   let notification = notifications[0];
   info("triggering command: " + notification.getAttribute("buttonlabel"));
 
@@ -69,7 +69,7 @@ function triggerSecondaryCommand(popup, win) {
   }
   info("triggering secondary command");
   let notifications = popup.childNodes;
-  ok(notifications.length > 0, "at least one notification displayed");
+  ok(notifications.length, "at least one notification displayed");
   let notification = notifications[0];
   EventUtils.synthesizeMouseAtCenter(notification.secondaryButton, {}, win);
 }

dom/indexedDB/test/test_third_party.html

@@ -85,7 +85,7 @@
         ok(false, 'Test has already received a message from ${message.source}');
       }
 
-      if (testFrames.length > 0) {
+      if (testFrames.length) {
         return;
       }
 

dom/l10n/tests/mochitest/document_l10n/test_connectRoot_webcomponent_lazy.html

@@ -39,7 +39,7 @@
         let label = this.shadowRoot.getElementById("label");
 
         let verifyL10n = () => {
-          if (label.textContent.length > 0) {
+          if (label.textContent.length) {
             window.removeEventListener("MozAfterPaint", verifyL10n);
             is(label.textContent, "Learn more", "localization content applied to element");
             firstWidgetTranslated = true;

dom/l10n/tests/mochitest/document_l10n/test_docl10n.html

@@ -18,15 +18,15 @@
 
     // Test for initial localization applied.
     let desc = document.getElementById("main-desc");
-    is(desc.textContent.length > 0, true);
+    is(!!desc.textContent.length, true);
 
     // Test for manual value formatting.
     let msg = await document.l10n.formatValue("id-heading");
-    is(msg.length > 0, true);
+    is(!!msg.length, true);
 
     // Test for mutations applied.
     let verifyL10n = () => {
-      if (label.textContent.length > 0) {
+      if (label.textContent.length) {
         window.removeEventListener("MozAfterPaint", verifyL10n);
         SimpleTest.finish();
       }

dom/l10n/tests/mochitest/document_l10n/test_docl10n.xhtml

@@ -21,15 +21,15 @@
 
     // Test for initial localization applied.
     let desc = document.getElementById("main-desc");
-    is(desc.textContent.length > 0, true);
+    is(!!desc.textContent.length, true);
 
     // Test for manual value formatting
     let msg = await document.l10n.formatValue("id-heading");
-    is(msg.length > 0, true);
+    is(!!msg.length, true);
 
     // Test for mutations applied.
     let verifyL10n = () => {
-      if (label.textContent.length > 0) {
+      if (label.textContent.length) {
         window.removeEventListener("MozAfterPaint", verifyL10n);
         SimpleTest.finish();
       }

dom/l10n/tests/mochitest/document_l10n/test_docl10n_lazy.html

@@ -26,7 +26,7 @@
     await document.l10n.ready;
 
     // Lazy initialized localization should translate the document.
-    is(desc.textContent.length > 0, true, "main-desc is translated");
+    is(!!desc.textContent.length, true, "main-desc is translated");
 
     document.head.removeChild(link);
 

dom/l10n/tests/mochitest/document_l10n/test_docl10n_removeResourceIds.html

@@ -17,7 +17,7 @@
     {
       // 1. An example message from aboutAddons should be available.
       let value = await document.l10n.formatValue("shortcuts-browserAction2");
-      is(value.length > 0, true, "localized value retrieved");
+      is(!!value.length, true, "localized value retrieved");
     }
 
     {
@@ -29,7 +29,7 @@
     {
       // 3. An example message from aboutSupport should still be available.
       let value = await document.l10n.formatValue("features-version");
-      is(value.length > 0, true, "localized value retrieved");
+      is(!!value.length, true, "localized value retrieved");
 
       // 4. An example message from aboutAddons should not be available.
       await document.l10n.formatValue("shortcuts-browserAction").then(

dom/l10n/tests/mochitest/document_l10n/test_docl10n_sync.html

@@ -15,15 +15,15 @@
 
     // Test for initial localization applied.
     let desc = document.getElementById("main-desc");
-    is(desc.textContent.length > 0, true);
+    is(!!desc.textContent.length, true);
 
     // Test for manual value formatting.
     let msg = await document.l10n.formatValue("id-heading");
-    is(msg.length > 0, true);
+    is(!!msg.length, true);
 
     // Test for mutations applied.
     let verifyL10n = () => {
-      if (label.textContent.length > 0) {
+      if (label.textContent.length) {
         window.removeEventListener("MozAfterPaint", verifyL10n);
         SimpleTest.finish();
       }

dom/l10n/tests/mochitest/dom_localization/test_connectRoot.html

@@ -29,11 +29,11 @@ key1 = Value for Key 1
     );
 
     await domLoc.translateRoots();
-    is(p1.textContent.length == 0, true);
+    is(!p1.textContent.length, true);
     const body = document.body;
     domLoc.connectRoot(body);
     await domLoc.translateRoots();
-    is(p1.textContent.length > 0, true);
+    is(!!p1.textContent.length, true);
 
     SimpleTest.finish();
   };

dom/l10n/tests/mochitest/dom_localization/test_connectRoot_webcomponent.html

@@ -24,7 +24,7 @@
 
         // Test for mutations applied.
         let verifyL10n = () => {
-          if (label.textContent.length > 0) {
+          if (label.textContent.length) {
             window.removeEventListener("MozAfterPaint", verifyL10n);
             // Notice: In normal tests we do not want to test against any particular
             // value as per https://firefox-source-docs.mozilla.org/intl/l10n/l10n/fluent_tutorial.html#testing

dom/l10n/tests/mochitest/dom_localization/test_disconnectRoot.html

@@ -30,7 +30,7 @@ key2 = Value for Key 2
     );
 
     await domLoc.translateRoots();
-    is(p1.textContent.length == 0, true);
+    is(!p1.textContent.length, true);
 
     const body = document.body;
 

dom/l10n/tests/mochitest/l10n_mutations/test_append_content_post_dcl.html

@@ -15,7 +15,7 @@
     document.l10n.setAttributes(elem, "crash-reports-title");
     is(elem.textContent.length, 0);
     let verifyL10n = () => {
-      if (elem.textContent.length > 0) {
+      if (elem.textContent.length) {
         window.removeEventListener("MozAfterPaint", verifyL10n);
         SimpleTest.finish();
       }

dom/l10n/tests/mochitest/l10n_mutations/test_append_content_pre_dcl.html

@@ -16,7 +16,7 @@
   document.l10n.setAttributes(elem, "crash-reports-title");
   is(elem.textContent.length, 0);
   let verifyL10n = () => {
-    if (elem.textContent.length > 0) {
+    if (elem.textContent.length) {
       window.removeEventListener("MozAfterPaint", verifyL10n);
       SimpleTest.finish();
     }

dom/l10n/tests/mochitest/l10n_mutations/test_append_fragment_post_dcl.html

@@ -24,7 +24,7 @@
     is(elem2.textContent.length, 0);
 
     let verifyL10n = () => {
-      if (elem.textContent.length > 0 && elem2.textContent.length > 0) {
+      if (elem.textContent.length && elem2.textContent.length) {
         window.removeEventListener("MozAfterPaint", verifyL10n);
         SimpleTest.finish();
       }

dom/l10n/tests/mochitest/l10n_mutations/test_pause_observing.html

@@ -23,9 +23,9 @@
     document.l10n.setAttributes(elem3, "crash-reports-title");
 
     let verifyL10n = () => {
-      if (elem1.textContent.length > 0 &&
+      if (elem1.textContent.length &&
-          elem2.textContent.length == 0 &&
+          !elem2.textContent.length &&
-          elem3.textContent.length > 0) {
+          elem3.textContent.length) {
         window.removeEventListener("MozAfterPaint", verifyL10n);
         SimpleTest.finish();
       }

dom/l10n/tests/mochitest/l10n_mutations/test_remove_element.html

@@ -48,17 +48,17 @@
     document.body.appendChild(elem3);
 
     // 1. `elem` should be localized since it is in DOM.
-    await SimpleTest.waitForCondition(() => elem.textContent.length > 0);
+    await SimpleTest.waitForCondition(() => elem.textContent.length);
     // 2. `elem2` was removed before l10n frame, so it should remain not localized.
     is(elem2.textContent.length, 0);
     // 3. `elem3` was added/removed/re-added so it should become localized.
-    await SimpleTest.waitForCondition(() => elem3.textContent.length > 0);
+    await SimpleTest.waitForCondition(() => elem3.textContent.length);
     // 4. `elem4` was not re-added, so it shouldn't be localized.
     is(elem4.textContent.length, 0);
 
     document.body.appendChild(elem4);
     // 5. Now we re-added `elem4` to DOM so it should get localized.
-    await SimpleTest.waitForCondition(() => elem4.textContent.length > 0);
+    await SimpleTest.waitForCondition(() => elem4.textContent.length);
     SimpleTest.finish();
   });
   </script>

dom/l10n/tests/mochitest/l10n_mutations/test_remove_fragment.html

@@ -44,20 +44,20 @@
     document.body.appendChild(div2);
 
     // 1. `elem` should be localized since it is in DOM.
-    await SimpleTest.waitForCondition(() => elem.textContent.length > 0);
+    await SimpleTest.waitForCondition(() => !!elem.textContent.length);
 
     // 2. `elem2` was removed before l10n frame, so it should remain not localized.
     is(elem2.textContent.length, 0);
 
     // 3. `elem3` was added/removed/re-added so it should become localized.
-    await SimpleTest.waitForCondition(() => elem3.textContent.length > 0);
+    await SimpleTest.waitForCondition(() => !!elem3.textContent.length);
 
     // 4. `elem4` was not re-added, so it shouldn't be localized.
     is(elem4.textContent.length, 0);
 
     document.body.appendChild(div);
     // 5. Now we re-added `elem4` to DOM so it should get localized.
-    await SimpleTest.waitForCondition(() => elem4.textContent.length > 0);
+    await SimpleTest.waitForCondition(() => !!elem4.textContent.length);
     SimpleTest.finish();
   });
   </script>

dom/l10n/tests/mochitest/l10n_mutations/test_set_attributes.html

@@ -21,7 +21,7 @@
     elem2.setAttribute("data-l10n-args", JSON.stringify({bug: "New string"}));
 
     let verifyL10n = () => {
-      if (elem.textContent.length > 0 && elem2.textContent.includes("New string")) {
+      if (elem.textContent.length && elem2.textContent.includes("New string")) {
         window.removeEventListener("MozAfterPaint", verifyL10n);
         SimpleTest.finish();
       }

dom/l10n/tests/mochitest/l10n_mutations/test_template.html

@@ -20,7 +20,7 @@
     document.body.appendChild(clone);
 
     let verifyL10n = () => {
-      if (span.textContent.length > 0) {
+      if (span.textContent.length) {
         window.removeEventListener("MozAfterPaint", verifyL10n);
         SimpleTest.finish();
       }

dom/l10n/tests/mochitest/l10n_overlays/test_same_id.html

@@ -26,7 +26,7 @@
     let inputElem = document.getElementById("search-input");
 
     // Test for initial localization applied.
-    is(inputElem.getAttribute("placeholder").length > 0, true);
+    is(!!inputElem.getAttribute("placeholder").length, true);
 
     let observer = new MutationObserver((mutations) => {
       for (let mutation of mutations) {

dom/l10n/tests/mochitest/l10n_overlays/test_same_id_args.html

@@ -26,7 +26,7 @@
     let inputElem = document.getElementById("search-input");
 
     // Test for initial localization applied.
-    is(inputElem.getAttribute("placeholder").length > 0, true);
+    is(!!inputElem.getAttribute("placeholder").length, true);
 
     let observer = new MutationObserver((mutations) => {
       for (let mutation of mutations) {

dom/media/PeerConnection.jsm

@@ -732,7 +732,7 @@ class RTCPeerConnection {
           "Missing required 'urls' member of RTCIceServer"
         );
       }
-      if (urls.length == 0) {
+      if (!urls.length) {
         throw new this._win.DOMException(
           `${msg} - urls is empty`,
           "SyntaxError"
@@ -1524,7 +1524,7 @@ class RTCPeerConnection {
   get currentLocalDescription() {
     this._checkClosed();
     const sdp = this._pc.currentLocalDescription;
-    if (sdp.length == 0) {
+    if (!sdp.length) {
       return null;
     }
     const type = this._pc.currentOfferer ? "offer" : "answer";
@@ -1534,7 +1534,7 @@ class RTCPeerConnection {
   get pendingLocalDescription() {
     this._checkClosed();
     const sdp = this._pc.pendingLocalDescription;
-    if (sdp.length == 0) {
+    if (!sdp.length) {
       return null;
     }
     const type = this._pc.pendingOfferer ? "offer" : "answer";
@@ -1548,7 +1548,7 @@ class RTCPeerConnection {
   get currentRemoteDescription() {
     this._checkClosed();
     const sdp = this._pc.currentRemoteDescription;
-    if (sdp.length == 0) {
+    if (!sdp.length) {
       return null;
     }
     const type = this._pc.currentOfferer ? "answer" : "offer";
@@ -1558,7 +1558,7 @@ class RTCPeerConnection {
   get pendingRemoteDescription() {
     this._checkClosed();
     const sdp = this._pc.pendingRemoteDescription;
-    if (sdp.length == 0) {
+    if (!sdp.length) {
       return null;
     }
     const type = this._pc.pendingOfferer ? "answer" : "offer";

dom/media/mediacontrol/tests/browser/head.js

@@ -299,7 +299,7 @@ async function isGivenTabUsingDefaultMetadata(tab, options = {}) {
   const fallbackTitle = await localization.formatValue(
     "mediastatus-fallback-title"
   );
-  ok(fallbackTitle.length > 0, "l10n fallback title is not empty");
+  ok(fallbackTitle.length, "l10n fallback title is not empty");
 
   const metadata = tab.linkedBrowser.browsingContext.mediaController.getMetadata();
 

dom/media/mediasource/test/test_LoadedDataFired_mp4.html

@@ -15,12 +15,12 @@ SimpleTest.waitForExplicitFinish();
 runWithMSE(async (ms, el) => {
   el.controls = true;
   el.addEventListener("loadeddata", () => {
-    ok(el.buffered.length > 0, "data is buffered");
+    ok(el.buffered.length, "data is buffered");
     is(el.buffered.start(0), 0, "must fire loadeddata when data has been loaded");
     is(el.currentTime, 0, "must fire loadeddata at start");
   });
   el.addEventListener("playing", () => {
-    ok(el.buffered.length > 0, "data is buffered");
+    ok(el.buffered.length, "data is buffered");
     is(el.buffered.start(0), 0, "must fire playing when data has been loaded");
     ok(el.currentTime >= 0, "must have started playback");
   });

dom/media/test/chrome/test_accumulated_play_time.html

@@ -567,7 +567,7 @@ async function checkReportedTelemetry(media, reportExpected, hasVideo, hasAudio,
        * }
        */
       const items = Object.entries(hist.snapshot());
-      if (items.length > 0) {
+      if (items.length) {
         for (const [key, value] of items) {
           const entriesNums = Object.entries(value.values).length;
           ok(reportExpected && entriesNums > 0, `Reported ${key} for ${name}`);
@@ -590,7 +590,7 @@ async function checkReportedTelemetry(media, reportExpected, hasVideo, hasAudio,
     const hist =
       SpecialPowers.Services.telemetry.getKeyedHistogramById("MEDIA_PLAY_TIME_MS");
     const items = Object.entries(hist.snapshot());
-    if (items.length > 0) {
+    if (items.length) {
       for (const item of items) {
         ok(item[0].includes("V") != -1 || !hasVideo, "Video time is reported if video was present");
       }
@@ -604,7 +604,7 @@ async function checkReportedTelemetry(media, reportExpected, hasVideo, hasAudio,
     try {
       const hist = SpecialPowers.Services.telemetry.getKeyedHistogramById(name);
       const items = Object.entries(hist.snapshot());
-      if (items.length > 0) {
+      if (items.length) {
         for (const [key, value] of items) {
           const entriesNums = Object.entries(value.values).length;
           ok(reportExpected && entriesNums > 0, `Reported ${key} for ${name}`);

dom/media/test/eme_standalone.js

@@ -241,10 +241,7 @@ var EmeHelper = class EmeHelper {
     if (!this._initDataTypes) {
       throw new Error("EmeHelper needs _initDataTypes to configure media");
     }
-    if (
+    if (!this._audioCapabilities.length && !this._videoCapabilities.length) {
-      this._audioCapabilities.length == 0 &&
-      this._videoCapabilities.length == 0
-    ) {
       throw new Error(
         "EmeHelper needs _audioCapabilities or _videoCapabilities to configure media"
       );

dom/media/test/manifest.js

@@ -2168,7 +2168,7 @@ function checkMetadata(msg, e, test) {
 // installed video backends.
 function getPlayableVideo(candidates) {
   var resources = getPlayableVideos(candidates);
-  if (resources.length > 0) {
+  if (resources.length) {
     return resources[0];
   }
   return null;
@@ -2186,7 +2186,7 @@ function getPlayableAudio(candidates) {
   var resources = candidates.filter(function(x) {
     return /^audio/.test(x.type) && v.canPlayType(x.type);
   });
-  if (resources.length > 0) {
+  if (resources.length) {
     return resources[0];
   }
   return null;
@@ -2341,7 +2341,7 @@ function MediaTestManager() {
     });
 
     SimpleTest.registerCleanupFunction(() => {
-      if (this.tokens.length > 0) {
+      if (this.tokens.length) {
         info("Test timed out. Remaining tests=" + this.tokens);
       }
       for (var token of this.tokens) {
@@ -2448,7 +2448,7 @@ function MediaTestManager() {
     if (
       this.testNum == this.tests.length &&
       !DEBUG_TEST_LOOP_FOREVER &&
-      this.tokens.length == 0 &&
+      !this.tokens.length &&
       !this.isShutdown
     ) {
       this.isShutdown = true;

dom/media/test/test_debug_data_helpers.html

@@ -56,7 +56,7 @@ add_task(async function testMozDebugReaderData() {
     "Audio track should have demuxed some samples"
   );
   ok(
-    debugData.demuxer.audioTrack.ranges.length > 0,
+    debugData.demuxer.audioTrack.ranges.length,
     "Audio track should have some buffered range"
   );
   ok(
@@ -64,7 +64,7 @@ add_task(async function testMozDebugReaderData() {
     "Video track should have demuxed some samples"
   );
   ok(
-    debugData.demuxer.videoTrack.ranges.length > 0,
+    debugData.demuxer.videoTrack.ranges.length,
     "Video track should have some buffered range"
   );
   removeNodeAndSource(video);

dom/media/test/test_decode_error.html

@@ -32,7 +32,7 @@ function startTest(test, token) {
       is(el.error.code, MediaError.MEDIA_ERR_DECODE, "Expected a decode error");
     }
     ok(typeof el.error.message === 'string' || el.error.message instanceof String, "Element 'message' attr expected to be a string");
-    ok(el.error.message.length > 0, "Element 'message' attr has content");
+    ok(el.error.message.length, "Element 'message' attr has content");
     el._sawError = true;
     manager.finished(token);
   });

dom/media/test/test_delay_load.html

@@ -96,7 +96,7 @@ v.onloadstart = function(e) {
 v.load(); // load started while in this document, this doc's load will block until
           // the video's finished loading (in the other document).
 
-if (gRegisteredElements.length > 0) {
+if (gRegisteredElements.length) {
   SimpleTest.waitForExplicitFinish();
 } else {
   todo(false, "No types supported");

dom/media/test/test_error_on_404.html

@@ -21,7 +21,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=476731
 var videos = [];
 
 function FinishedLoads() {
-  if (videos.length == 0)
+  if (!videos.length)
     return false;
   for (var i=0; i<videos.length; ++i) {
     if (videos[i]._loadedData) {
@@ -73,7 +73,7 @@ for (var i=0; i<g404Tests.length; ++i) {
    videos.push(v);
 }
 
-if (videos.length == 0) {
+if (!videos.length) {
   todo(false, "No types supported");
 } else {
   SimpleTest.waitForExplicitFinish();

dom/media/test/test_fastSeek.html

@@ -75,7 +75,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=778077
       v.target = 0;
       v.keyframes = test.keyframes;
       v.keyframeIndex = 0;
-      ok(v.keyframes.length > 0, v.name + " - video should have at least one sync point");
+      ok(v.keyframes.length, v.name + " - video should have at least one sync point");
       v.addEventListener("loadedmetadata", onloadedmetadata);
       v.addEventListener("seeked", onseeked);
       document.body.appendChild(v);

dom/media/test/test_referer.html

@@ -76,7 +76,7 @@ for (var i=0; i<gSmallTests.length; ++i) {
   media.push(v);
 }
 
-if (media.length == 0) {
+if (!media.length) {
   todo(false, "No types supported");
 } else {
   SimpleTest.waitForExplicitFinish();

dom/media/test/test_source.html

@@ -25,7 +25,7 @@ is(a1.childNodes.length, 0, "should have no children");
 
 function newSource(filter) {
   var candidates = gSmallTests.filter(function(x){return filter.test(x.type);});
-  if (candidates.length > 0) {
+  if (candidates.length) {
     var e = document.createElement("source");
     e.type = candidates[0].type;
     e.src = candidates[0].name;

dom/media/test/test_standalone.html

@@ -49,7 +49,7 @@ function doTest()
   SimpleTest.finish();
 }
 
-if (iframes.length == 0) {
+if (!iframes.length) {
   todo(false, "No types supported");
 } else {
   SimpleTest.waitForExplicitFinish();

dom/media/test/test_streams_element_capture.html

@@ -84,7 +84,7 @@ async function startTest(test, token) {
     `${token} checking readyState`);
   ok(vout.ended, `${token} checking playback has ended`);
   isnot(stream.getTracks().length, 0, `${token} results in some tracks`);
-  if (stream.getVideoTracks().length > 0) {
+  if (stream.getVideoTracks().length) {
     ok(test.type.match(/^video/), `${token} is a video resource`);
     checkDrawImage(vout, `${token} checking video frame pixel has been drawn`);
   }

dom/media/test/test_unseekable.html

@@ -85,7 +85,7 @@ function startTest(test, token) {
 function canPlay(candidates) {
   var v = document.createElement("video");  
   var resources = candidates.filter(function(x){return v.canPlayType(x.type);});
-  return (resources.length > 0);
+  return (resources.length);
 }
 
 if (canPlay(gUnseekableTests)) {

dom/media/webaudio/test/test_AudioNodeDevtoolsAPI.html

@@ -33,7 +33,7 @@
     if (index != -1) {
       info("Dropping id " + id + " at index " + index);
       ids.splice(index, 1);
-      if (ids.length == 0) {
+      if (!ids.length) {
         SimpleTest.executeSoon(function() {
           is(weak.get(), null, "The weak reference must be dropped now");
           SpecialPowers.removeObserver(observer, "webaudio-node-demise");

dom/media/webaudio/test/test_ScriptProcessorCollected1.html

@@ -54,7 +54,7 @@ testProcessor.onaudioprocess = function(event) {
       SpecialPowers.removeObserver(observer, "webaudio-node-demise");
       observer = null;
       event.target.onaudioprocess = null;
-      ok(ids.length == 0, "All expected nodes should be collected");
+      ok(!ids.length, "All expected nodes should be collected");
       SimpleTest.finish();
     });
     break;

dom/media/webaudio/test/test_bug1027864.html

@@ -17,7 +17,7 @@ function observer(subject, topic, data) {
   if (index != -1) {
     ok(true, "Dropping id " + id + " at index " + index);
     ids.splice(index, 1);
-    if (ids.length == 0) {
+    if (!ids.length) {
       SimpleTest.executeSoon(function() {
         SimpleTest.finish();
       });

dom/media/webaudio/test/webaudio.js

@@ -253,7 +253,7 @@ function runTest() {
           var expectedBuffer = expectedBuffers.shift();
           testLength += expectedBuffer.length;
           compareBuffers(e.inputBuffer, expectedBuffer);
-          if (expectedBuffers.length == 0) {
+          if (!expectedBuffers.length) {
             sp.onaudioprocess = null;
             callback();
           }

dom/media/webrtc/tests/mochitests/pc.js

@@ -1626,9 +1626,9 @@ PeerConnectionWrapper.prototype = {
       info(
         this.label + ": iceCandidate = " + JSON.stringify(anEvent.candidate)
       );
-      ok(anEvent.candidate.sdpMid.length > 0, "SDP mid not empty");
+      ok(anEvent.candidate.sdpMid.length, "SDP mid not empty");
       ok(
-        anEvent.candidate.usernameFragment.length > 0,
+        anEvent.candidate.usernameFragment.length,
         "usernameFragment not empty"
       );
 

dom/media/webrtc/tests/mochitests/sdpUtils.js

@@ -138,7 +138,7 @@ var sdputils = {
     ).filter(hasOwnTransport);
 
     ok(
-      msectionsWithOwnTransports.length > 0,
+      msectionsWithOwnTransports.length,
       "SDP should contain at least one msection with a transport"
     );
     msectionsWithOwnTransports.forEach(checkForTransportAttributes);

dom/media/webrtc/tests/mochitests/templates.js

@@ -131,7 +131,7 @@ function dumpSdp(test) {
 // We need to verify that at least one candidate has been (or will be) gathered.
 function waitForAnIceCandidate(pc) {
   return new Promise(resolve => {
-    if (!pc.localRequiresTrickleIce || pc._local_ice_candidates.length > 0) {
+    if (!pc.localRequiresTrickleIce || pc._local_ice_candidates.length) {
       resolve();
     } else {
       // In some circumstances, especially when both PCs are on the same
@@ -142,7 +142,7 @@ function waitForAnIceCandidate(pc) {
     }
   }).then(() => {
     ok(
-      pc._local_ice_candidates.length > 0,
+      pc._local_ice_candidates.length,
       pc + " received local trickle ICE candidates"
     );
     isnot(

dom/media/webrtc/tests/mochitests/test_enumerateDevices.html

@@ -47,7 +47,7 @@ runTest(async () => {
   // Validate enumerated devices.
 
   let devices = await navigator.mediaDevices.enumerateDevices();
-  ok(devices.length > 0, "At least one device found");
+  ok(devices.length, "At least one device found");
   let jsoned = JSON.parse(JSON.stringify(devices));
   is(jsoned[0].kind, devices[0].kind, "kind survived serializer");
   is(jsoned[0].deviceId, devices[0].deviceId, "deviceId survived serializer");

dom/media/webrtc/tests/mochitests/test_peerConnection_audioSynchronizationSources.html

@@ -17,8 +17,8 @@
     is(receivers.length, 2, "Expected number of receivers");
     // Wait for sync sources
     while (true) {
-        if (receivers[0].getSynchronizationSources().length > 0 &&
+        if (receivers[0].getSynchronizationSources().length &&
-            receivers[1].getSynchronizationSources().length > 0) {
+            receivers[1].getSynchronizationSources().length) {
         break;
       }
       await wait(250);

dom/media/webrtc/tests/mochitests/test_peerConnection_audioSynchronizationSourcesUnidirectional.html

@@ -15,7 +15,7 @@
     let receiver = test.pcRemote.getReceivers()[0];
     ok(receiver, "Remote has a receiver");
     // Wait for remote sync source
-    while (receiver.getSynchronizationSources().length == 0) {
+    while (!receiver.getSynchronizationSources().length) {
       await wait(250);
     }
     is(receiver.getSynchronizationSources().length, 1,
@@ -32,7 +32,7 @@
     await waitForSyncSources(test);
     let receiver = test.pcRemote.getReceivers()[0];
     let syncSources = receiver.getSynchronizationSources();
-    ok(syncSources.length > 0,
+    ok(syncSources.length,
        "Receiver has Synchronization sources " + JSON.stringify(syncSources));
     is(syncSources.length, 1, "Receiver has only a single sync source");
     let syncSource = syncSources[0];

dom/media/webrtc/tests/mochitests/test_peerConnection_capturedVideo.html

@@ -55,8 +55,8 @@
         offerToReceiveAudio: false,
       }
     );
-    const hasVideo = stream.getVideoTracks().length > 0;
+    const hasVideo = !!stream.getVideoTracks().length;
-    const hasAudio = stream.getAudioTracks().length > 0;
+    const hasAudio = !!stream.getAudioTracks().length;
     test.setMediaConstraints([{ video: hasVideo, audio: hasAudio }], []);
     test.chain.replace("PC_LOCAL_GUM", [
       function PC_LOCAL_CAPTUREVIDEO(test) {

dom/media/webrtc/tests/mochitests/test_peerConnection_insertDTMF.html

@@ -13,7 +13,7 @@ createHTML({
 });
 
 function insertdtmftest(pc) {
-  ok(pc.getSenders().length > 0, "have senders");
+  ok(pc.getSenders().length, "have senders");
   var sender = pc.getSenders()[0];
   ok(sender.dtmf, "sender has dtmf object");