regulex/README.md

JavaScript Regular Expression Parser and Visualizer.

# Regulex

[Regulex](https://jex.im/regulex/) is a JavaScript Regular Expression Parser & Visualizer.

**This is the legacy version!**

### Features

- Written in pure JavaScript. No backend required.
- You can embed the graph on 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 allow octal escape in string, but many browsers still allow octal escape in regex. 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.

### Install for Node.js
```
npm install regulex
```


### Build for Browser
This command will generate bundle `dist/regulex.js` for browser side:
```bash
npm install -g requirejs
r.js -o build-config.js
```

### API

#### Parse to AST

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

#### Visualize

```javascript
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("yourSvgContainerId", 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;
}
```