Code working in browser console but not in tampermonkey

Question

I am trying to run the following block of code on https://lichess.org/uZIjh0SXxnt5.

var x = document.getElementsByTagName(\"a\");

for(var i = 0; i < x.le         


        

Answer 1

Most of that page is loaded dynamically (AJAX-driven), which means that your script will normally finish running long before the nodes, that you are interested in, appear in/on the page.

You must use AJAX-aware techniques such as waitForKeyElements or MutationObserver.

Here's a complete Tampermonkey script that illustrates the process:

// ==UserScript==
// @name     _Lichess.org, Glorify select users
// @match    *://lichess.org/*
// @require  https://ajax.googleapis.com/ajax/libs/jquery/2.1.0/jquery.min.js
// @require  https://gist.github.com/raw/2625891/waitForKeyElements.js
// @grant    GM_addStyle
// @grant    GM.getValue
// ==/UserScript==
//- The @grant directives are needed to restore the proper sandbox.

waitForKeyElements ("a[href*='WaisKamal']", spiffifyLink);

function spiffifyLink (jNode) {
    var oldHtml = jNode.html ();
    var newHtml = '<span class="title" data-title="GM" title="Grandmaster">GM</span> ' + oldHtml;
    jNode.html (newHtml);
}

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See this other answer for more information about choosing and using waitForKeyElements and/with jQuery selectors.