Regulex

Regulex is a JavaScript Regular Expression Parser & Visualizer.

Features

Written in pure JavaScript. No backend needed.
You can embed the graph in you own site through HTML iframe element.
Detailed error message. In most cases it can point out the precise syntax error position.
No support for octal escape. Yes it is a feature. ECMAScript strict mode doesn't support octal escape in string, but many browsers still support octal escape in regex. I make things easier. In regulex, DecimalEscape will always be treated as back reference. If the back reference is invalid, e.g. /\1/, /(\1)/, /(a)\2/, or DecimalEscape appears in charset（because in this case it can't be explained as back reference, e.g. /(ab)[\1]/, Regulex will always throw an error.

Build

This command will generate dest/regulex.js.

npm install -g requirejs
r.js -o build-config.js

API

Parse to AST

var parse = require("regulex").parse;
var re = /var\s+([a-zA-Z_]\w*);/ ;
console.log(parse(re.source));

Visualize

var parse = require("regulex").parse;
var visualize = require("regulex").visualize;
var Raphael = require('regulex').Raphael;
var re = /var\s+([a-zA-Z_]\w*);/;
var paper = Raphael("yourSvgContainer", 0, 0);
try {
  visualize(parse(re.source), getRegexFlags(re), paper);
} catch(e) {
  if (e instanceof parse.RegexSyntaxError) {
    logError(re, e);
  } else {
    throw e;
  }
}

function logError(re, err) {
  var msg = ["Error:" + err.message, ""];
  if (typeof err.lastIndex === "number") {
    msg.push(re);
    msg.push(new Array(err.lastIndex).join("-") + "^");
  }
  console.log(msg.join("\n"));
}


function getRegexFlags(re) {
  var flags = "";
  flags += re.ignoreCase ? "i" : "";
  flags += re.global ? "g" : "";
  flags += re.multiline ? "m" : "";
  return flags;
}

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