JS-Lex

What Is It?

A lexer generator written in JavaScript that uses the language’s regular expression engine to perform its analysis.

Usage

For anyone familiar with lex, flex, and friends the syntax is familiar enough. The following will create a lexer that will tokenize a JavaScript-like text. A full example can be found in the repository.

var rules = [
    [/(?:"((?:\\.|[^"])*)"|'((?:\\.|[^'])*)')/, 'STRING'
    , function (token) {
        token.value = (token.match[1] || token.match[2] || '')
            .replace(/\\(?:u([0-9a-fA-F]{4})|x([0-9a-fA-F]{2})|([0-3][0-7]{0,2}|[0-7]{1,2})|(.))/g, function () {
              var match = arguments;
              var c;
              if (c = match[1] || match[2]) {
                return String.fromCharCode(parseInt(c, 16));
              } else if (c = match[3]) {
                return String.fromCharCode(parseInt(c, 8));
              } else {
                c = match[4];
                if (Object.prototype.hasOwnProperty.call(ESCAPES, c)) {
                  return ESCAPES[c];
                } else {
                  return c;
                }
              }
            });
      }]
  , [/([_a-zA-Z][_a-zA-Z0-9]*)\(/, 'FUNC'
    , function (token) {
        token.value = token.match[1];
      }]
  , [/[+-]?(?:(0x[0-9a-fA-F]+|0[0-7]+)|((?:[0-9]+(?:\.[0-9]*)?|\.[0-9]+)(?:[eE][+-]?[0-9]+)?|NaN|Infinity))/, 'NUM'
    , function (token) {
        if (token.match[1]) {
          token.value = parseInt(token.match[0]);
        } else {
          token.value = parseFloat(token.match[0]);
        }
      }]
  , [/\)/, 'RPAREN']
  , [/;/, 'SEMI']
  , [/,/, 'COMMA']
  , [/\s+/, null]
  ];

lexer = new Lexer(rules);

Notes

At the moment, Lexer does not support macros (the definitions section for users of lex).

License

Released under zlib

Copyright (C) 2010 Chad Weider

This software is provided 'as-is', without any express or implied
warranty. In no event will the authors be held liable for any damages
arising from the use of this software.

Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it
freely, subject to the following restrictions:

1. The origin of this software must not be misrepresented; you must not
   claim that you wrote the original software. If you use this software in
   a product, an acknowledgment in the product documentation would be
   appreciated but is not required.
2. Altered source versions must be plainly marked as such, and must not be
   misrepresented as being the original software.
3. This notice may not be removed or altered from any source distribution.