More documentation for the javascript

common/static/js/capa/symbolic_mathjax_preprocessor.js

+/* This file defines a processor in between the student's math input
+   (AsciiMath) and what is read by MathJax. It allows for our own
+   customizations, such as use of the syntax "a_b__x" in superscripts, or
+   possibly coloring certain variables, etc&.
+
+   It is used in the <textline> definition like the following:
+
+     <symbolicresponse expect="a_b^c + b_x__d" size="30">
+       <textline math="1"
+         preprocessorClassName="SymbolicMathjaxPreprocessor"
+	 preprocessorSrc="/static/js/capa/symbolic_mathjax_preprocessor.js"/>
+     </symbolicresponse>
+*/
 window.SymbolicMathjaxPreprocessor = function () {
   this.fn = function (eqn) {
     // flags and config
@@ -14,7 +27,7 @@ window.SymbolicMathjaxPreprocessor = function () {
       eqn = eqn.replace(/__(?:([^\{])|\{([^\}]+)\})/g, '^{' + c + '$1$2}');
 
       // NOTE: MathJax supports '\class{name}{mathcode}' but not for asciimath
-	// input, which is too bad. This would be preferable to the char tag
+      // input, which is too bad. This would be preferable to this char tag
     }
 
     return eqn;