TamperMonkey userscript doesn't fire DOMContentLoaded event

Question

This is a TamperMonkey userscript. Why doesn't "HELLO" popup? I am running Google Chrome on Ubuntu.

// ==UserScript==
// @name         New Userscript
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  try to take over the world!
// @author       You
// @match        http://*/*
// @match        https://*/*
// @grant        none
// ==/UserScript==

window.addEventListener("DOMContentLoaded", function(event) {
    alert("HELLO");
  });

[`document`, not `window`](https://developer.mozilla.org/en-US/docs/Web/Events/DOMContentLoaded). — Patrick Roberts, Jun 13 '16 at 19:59
For a basis of comparison, just doing `alert("HELLO");` works. — Joshua Meyers, Jun 13 '16 at 20:01
add `// @run-at document-start` to your header will help, check out [the specification](https://wiki.greasespot.net/Metadata_Block#.40run-at) for more details — tsh, Jun 15 '16 at 15:27

score 10 · Accepted Answer · edited May 23 '17 at 11:58

10

Use this:

// ==UserScript==
// @name         New Userscript
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  try to take over the world!
// @author       You
// @match        http://*/*
// @grant        none
// ==/UserScript==

(function() {
    'use strict';

    if (document.readyState == "complete" || document.readyState == "loaded" || document.readyState == "interactive") {
        alert("Already Loaded");
    } else {
        document.addEventListener("DOMContentLoaded", function(event) {
            alert("Just Loaded");
        });
    }
})();

Borrowed from How to detect if DOMContentLoaded was fired.

edited May 23 '17 at 11:58

Community

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answered Jun 13 '16 at 20:08

Patrick Roberts

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Thanks, this works. Is the problem that DOMContentLoaded fires before TamperMonkey starts running on the page? – Joshua Meyers Jun 13 '16 at 20:11
@JoshuaMeyers that is correct, as you should be able to deduce from the alerted text. – Patrick Roberts Jun 13 '16 at 20:12

TamperMonkey userscript doesn't fire DOMContentLoaded event

1 Answers1