Expand Macros

HTML

<button id="run">Expand Macros</button>
<textarea id="input">
\documentclass{amsart} 
\usepackage{amsmath,amssymb}
\newcommand{\N}{\mathbb{N}}
\DeclareMathOperator{\End}{End}

\begin{document}
In this lecture we'll study the ring of Endomorphisms of an Abelian group $A$.
Let's denote this ring by $\End(A)$. Throughout the lecture, $\N$ will denote
the set of natural numbers.
\end{document}
</textarea>
<textarea id="output">Output</textarea>

CSS

html, body {
  height: 90%;
}
button {
  display: block;
}
textarea {
  float: left;
  width: 48%;
  height: 80%;
}

JavaScript

function expandMacros(tex) {
    function nestBrackets(level) {
        var level = level || 5, re = c = "(?:[^\\r\\n\\{\\}]|\\\\[\\{\\}]|\\r?\\n(?!\\r?\\n))*?";
        while (level--) re = c + "(?:\\{" + re + "\}" + c + ")*?";
        return " *(\\{" + re + "\\}|[^\\{])";
    }    
    function getRegExp(name, macro) {
        var num = macro.num, def = macro.def, re = "";
        while (num--) re += nestBrackets();
        re = "\\" + name + "(?![a-zA-Z\\}])" + re;
        return new RegExp(re, "g");
    }
    function trimString(s) {
        return s.replace(/^ +| +$/g, '').replace(/^\{|\}$/g, "");
    }
    function extractMacros() {
        var cs = "\\\\\\w+", re;
        // \def, \gdef, \edef and \xdef
        re = new RegExp("\\\\[gex]?def\\*? *(" + cs + ") *(#\\d)*" + nestBrackets(), "g");
        tex = tex.replace(re, function(match){
            var m = arguments;
            var macro = {
                num:  m[2] ? Math.min(m[2].length / 2, 9) : 0,
                def:  trimString(m[3])
            };
            macros[trimString(m[1])] = macro;
            return "";
        });
        // \newcommand, \newcommand*, \renewcommand and \renewcommand*
        re = new RegExp("\\\\(?:re)?newcommand\\*? *(" + cs + "|\\{" + cs + "\}) *(\\[(\\d)\\])?"
                        + nestBrackets(), "g");
                        
        console.log(re)
        tex = tex.replace(re, function(match){
            var m = arguments;
            var macro = {
                num:  m[3] || 0,
                def:  trimString(m[4])
            };
            macros[trimString(m[1])] = macro;
            return "";
        });
        // \DeclareMathOperator and \DeclareMathOperator* inside amsmath
        re = new RegExp("\\\\DeclareMathOperator(\\*?) *(" + cs + "|\\{" + cs + "\}) *"
                        + nestBrackets(), "g");
        tex = tex.replace(re, function(match){
            var m = arguments;
            var macro = {
                num:  0,
        ...