CodeMirror 2: JavaScript mode

-// Demo code (the actual new parser character stream implementation)
-
-function StringStream(string) {
-  this.pos = 0;
-  this.string = string;
-}
-
-StringStream.prototype = {
-  done: function() {return this.pos >= this.string.length;},
-  peek: function() {return this.string.charAt(this.pos);},
-  next: function() {
-    if (this.pos < this.string.length)
-      return this.string.charAt(this.pos++);
-  },
-  eat: function(match) {
-    var ch = this.string.charAt(this.pos);
-    if (typeof match == "string") var ok = ch == match;
-    else var ok = ch && match.test ? match.test(ch) : match(ch);
-    if (ok) {this.pos++; return ch;}
-  },
-  eatWhile: function(match) {
-    var start = this.pos;
-    while (this.eat(match));
-    if (this.pos > start) return this.string.slice(start, this.pos);
-  },
-  backUp: function(n) {this.pos -= n;},
-  column: function() {return this.pos;},
-  eatSpace: function() {
-    var start = this.pos;
-    while (/\s/.test(this.string.charAt(this.pos))) this.pos++;
-    return this.pos - start;
-  },
-  match: function(pattern, consume, caseInsensitive) {
-    if (typeof pattern == "string") {
-      function cased(str) {return caseInsensitive ? str.toLowerCase() : str;}
-      if (cased(this.string).indexOf(cased(pattern), this.pos) == this.pos) {
-        if (consume !== false) this.pos += str.length;
-        return true;
-      }
-    }
-    else {
-      var match = this.string.slice(this.pos).match(pattern);
-      if (match && consume !== false) this.pos += match[0].length;
-      return match;
-    }
-  }
-};
-

JavaScript mode supports a single configuration - option, json, which will set the mode to expect JSON - data rather than a JavaScript program.