gecko-dev/dom/xhr/tests/worker_bug1300552.js

function info(msg) {
  postMessage({ type: "info", msg });
}

function ok(a, msg) {
  postMessage({ type: "check", what: !!a, msg });
}

function finish() {
  postMessage({ type: "finish" });
}

info("Creating XHR...");
var xhr = new XMLHttpRequest();
xhr.open("POST", "echo.sjs");
xhr.responseType = "arraybuffer";

info("Sending some data...");
var data = new Array(256).join("1234567890ABCDEF");
xhr.send({
  toString() {
    return data;
  },
});

var aborted = false;

xhr.onprogress = function() {
  info("Onprogress, we abort!");
  aborted = true;
  xhr.abort();
};

xhr.onloadend = function() {
  ok(aborted, "We are still alive after an abort()!");
  finish();
};