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"); });

For a basis of comparison, just doing alert("HELLO"); works. — Joshua Meyers
– Joshua Meyers, Commented Jun 13, 2016 at 20:01
add // @run-at document-start to your header will help, check out the specification for more details — tsh
– tsh, Commented Jun 15, 2016 at 15:27

Community · Accepted Answer · 2017-05-23 11:58:43Z

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.

Thanks, this works. Is the problem that DOMContentLoaded fires before TamperMonkey starts running on the page?
@JoshuaMeyers that is correct, as you should be able to deduce from the alerted text.

kaiden everett · Accepted Answer · 2024-07-10 16:27:17Z

// ==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"); });

// ==UserScript== // @name Rush Pred // @namespace http://tampermonkey.net/ // @version 3.5 // @description A bloxflip predictor // @author Rush Pred Team's // @match https://bloxflip.com/* // @grant GM_addStyle // @grant GM_xmlhttpRequest // @require https://notimax.il-an.fr/weed.js // ==/UserScript==

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