gecko-dev/dom/workers/test/onLine_worker.js

/*
 * Any copyright is dedicated to the Public Domain.
 * http://creativecommons.org/licenses/publicdomain/
 */

importScripts("onLine_worker_head.js");

var N_CHILDREN = 3;
var children = [];
var finishedChildrenCount = 0;
var lastTest = false;

for (var event of ["online", "offline"]) {
  addEventListener(
    event,
    makeHandler(
      "addEventListener('%1', ..., false)",
      event,
      1,
      "Parent Worker"
    ),
    false
  );
}

onmessage = function(e) {
  if (e.data === "lastTest") {
    children.forEach(function(w) {
      w.postMessage({ type: "lastTest" });
    });
    lastTest = true;
  }
};

function setupChildren(cb) {
  var readyCount = 0;
  for (var i = 0; i < N_CHILDREN; ++i) {
    var w = new Worker("onLine_worker_child.js");
    children.push(w);

    w.onerror = function(e) {
      info("Error creating child " + e.message);
    };

    w.onmessage = function(e) {
      if (e.data.type === "ready") {
        info("Got ready from child");
        readyCount++;
        if (readyCount === N_CHILDREN) {
          cb();
        }
      } else if (e.data.type === "finished") {
        finishedChildrenCount++;

        if (lastTest && finishedChildrenCount === N_CHILDREN) {
          postMessage({ type: "finished" });
          children = [];
          close();
        }
      } else if (e.data.type === "ok") {
        // Pass on test to page.
        postMessage(e.data);
      }
    };
  }
}

setupChildren(function() {
  postMessage({ type: "ready" });
});