skip-regex

skipRegex

Micro parser for detection of literal regexes.

• Fast detection with high accuracy.
• Minimum size.
• Compatible with NodeJS, bundlers, IE9+, and modern Browsers.
• TypeScript definition.
• Zero dependencies.

Install

npm install skip-regex --save
# or
yarn add skip-regex

or load the global skipRegex function in your browser:

<script src="https://unpkg.com/skip-regex/index.min.js"></script>

Three formats transpiled to ES5:

• CommonJS for node.js and browserify-like bundlers.
• ESM for bundlers like Rollup.
• UMD for AMD, CommonJS, and browsers.

Syntax

skipRegex(source: string, start: number) => number

The start position must point to a slash within source.

From there, skipRegex will find the end of a regular expression in the given string.

The returned value is the position of the character following the regex, or start+1 if the slash does not start a regex.

Example

This is a silly example, but it will give the idea.

import skipRegex from 'skip-regex'

const source = ' /.*/ '
const start  = source.indexOf('/')

if (~start) {
  const end = skipRegex(source, start)

  if (end > start + 1) {      // detected as regex?
    const regex = source.slice(start, end)
    console.log(`Found regex ${regex} at position ${start}!`)

  } else if (source[end] === '*' || source[end] === '/') {
    console.log('The slash starts a JS comment.')

  } else {
    console.log('The slash is a division sign.')
  }
}

For something more complete see the js-cleanup code, an utility to clean comments safely in JS-like sources, which uses skip-regex to skip regular expressions.

For Rollup, you can use rollup-plugin-node-resolve to resolve 'skip-regex' as an ES6 module.

For TypeScript, enable esModuleInterop in your tsconfig.json or use the "import=require" syntax:

import skipRegex = require('skip-regex')

//...

Related Links

Some sites and tools that have been helpful:

• RegExp (Regular Expressions) Objects : ECMA Specs
• RegExp on MDN : MDN Reference
• RegEgg : Complete tutorial, various regex dialects
• RegExr : Online tool for learn and test regexes
• RegExp Preview and Editor : VSCode extension based on regexper-static

Support my Work

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Licence

The MIT license (MIT)

© 2018 Alberto Martínez

Changelog

[1.0.2] - 2018-12-24

Added

• Adds of to the keywords that can precede a regex.
• Support for the s (ES9 "dotAll") flag.
• Related links in the Readme.