This is the ignore-whitespace of https://github.com/qfox/zeparser2/commit/86313d79ffafc21a3a71a4b8f1505d3269e0735b This diff is causing my parser to slow down by about 100% (in Chrome, at least) ... Crazy.

gistfile1.diff

diff --git a/src/par.js b/src/par.js
index 2a3507e..bef9db8 100644
--- a/src/par.js
+++ b/src/par.js
@@ -1,4 +1,7 @@
-if (typeof Tok === 'undefined') var Tok = require(__dirname+'/tok.js').Tok;
+
+
+(function(exports){
+  var Tok = exports.Tok || require(__dirname+'/tok.js').Tok;
 
 // indices match slots of the start-regexes (where applicable)
 // this order is determined by regex/parser rules so they are fixed
@@ -20,14 +23,13 @@ var ASI = 15;
 var ERROR = 16;
 var WHITE = 18; // WHITE_SPACE, LINETERMINATOR COMMENT_SINGLE COMMENT_MULTI
 
-var Par = function(input){
+  var Par = exports.Par = function(input){
     this.tok = new Tok(input);
 };
 
 Par.prototype = {
   run: function(){
     // prepare
-//    if (this.tok.input === '500') debugger
     this.tok.nextExpr();
     // go!
     this.parseStatements(false, false, false, []);
@@ -1059,4 +1061,4 @@ Par.prototype = {
   },
 };
 
-if (typeof exports === 'object') exports.Par = Par;
+})(typeof exports === 'object' ? exports : window);
diff --git a/src/tok.js b/src/tok.js
index 6f5becc..e7e42ce 100644
--- a/src/tok.js
+++ b/src/tok.js
@@ -1,3 +1,5 @@
+(function(exports){
+
 // indices match slots of the start-regexes (where applicable)
 // this order is determined by regex/parser rules so they are fixed
 var WHITE_SPACE = 1;
@@ -28,7 +30,7 @@ var WHITE = 18; // WHITE_SPACE, LINETERMINATOR COMMENT_SINGLE COMMENT_MULTI
  * @constructor
  * @param {string} input
  */
-var Tok = function(input){
+  var Tok = exports.Tok = function(input){
   this.tokens = [];
 
   this.input = (input||'');
@@ -54,6 +56,7 @@ var Tok = function(input){
 };
 
 // reverse lookup (only used for error messages..)
+
 Tok[WHITE_SPACE] = 'whitespace';
 Tok[LINETERMINATOR] = 'lineterminator';
 Tok[COMMENT_SINGLE] = 'comment_single';
@@ -173,7 +176,6 @@ Tok.prototype = {
    * possibly expecting a division (so not
    * a regex).
    *
-   * @param {number} type
    * @return {boolean}
    */
   nextPuncIfValue: function(){
@@ -824,4 +826,4 @@ Tok.prototype = {
   },
 };
 
-if (typeof exports === 'object') exports.Tok = Tok;
+})(typeof exports === 'object' ? exports : window);
(END)

(It was due to using an object literal as prototype object, which is bugged in chrome and deoptimizes)