KaTeX for Gists user extension

KaTeX_for_Gists.user.js

// ==UserScript==
// @name         KaTeX for Gists
// @author       Goran Topić
// @homepage     http://github.com/amadanmath/
// @include      *://gist.github.com/*
// @version      0.1.1
// @updateURL    https://gist.github.com/amadanmath/6eaf4cc850f38b78562f/raw/KaTeX_for_Gists.user.js
// @downloadURL  https://gist.github.com/amadanmath/6eaf4cc850f38b78562f/raw/KaTeX_for_Gists.user.js
// @description  Shows LaTeX in <tt> tags on Github Gist pages
// ==/UserScript==


(function() {
    var cdnBase = "https://cdnjs.cloudflare.com/ajax/libs/KaTeX/0.1.0/";

    function katexify(math) {
        var mathtext = math.innerHTML,
            block = false,
            mathtext, mathhtml;
        try {
            mathhtml = katex.renderToString(mathtext);
            math.innerHTML = mathhtml;
	        if (mathtext.match(/^\s*\\displaystyle/)) {
                math.className += " block";
    	    }
        } catch (e) {
            console.error(e.message);
        }
    }
    
    function loadKatexStyle() {
        GM_xmlhttpRequest({
            method: "GET",
            url: cdnBase + "katex.min.css",
            headers: {
                 "Content-Type": "application/javascript"
            },
            onload: function katexStyleLoaded(response) {
                var head, style, styletext;
                head = document.getElementsByTagName('head')[0];
                style = document.createElement('style');
                style.type = 'text/css';
                styletext = response.responseText.replace(
                    /url\((.*?)\)/g,
                    "url(" + cdnBase + "$1)"
                );
                styletext += "\n tt.block { display: inline-block; }"
                style.innerHTML = styletext;
                head.appendChild(style);
            }
        });
    }
    
    function loadKatexCode() {
        GM_xmlhttpRequest({
            method: "GET",
            url: cdnBase + "katex.min.js",
            headers: {
                 "Content-Type": "application/javascript"
            },
            onload: function katexCodeLoaded(response) {
                eval(response.responseText);
                for (var i = 0, len = maths.length; i < len; i++) {
                    katexify(maths[i]);
                }
            }
        });
    }
    
    var maths = document.querySelectorAll('tt');
    if (maths.length) {
        loadKatexStyle();
        loadKatexCode();
    }
})();