verbose-regexp

verbose-regexp

This module provides a way to use verbose regular expressions in JavaScript and TypeScript, similar to re.VERBOSE in Python. It provides that white-space at the start and end of lines are ignored, as are newlines, and anything following // to the end of the line.

It allows you to easily write multi-line regular expressions, and to make your regular expressions more self-documenting using formatting and comments.

Example:

    import { rx } from 'verbose-regexp'
    // or: const { rx } = require('verbose-regexp')

    const dateTime = rx`
      (\d{4}-\d{2}-\d{2}) // date
      T                   // time separator
      (\d{2}:\d{2}:\d{2}) // time
    `
    console.log(dateTime.exec(new Date().toISOString()))

You can also embed regular expressions within each other, to allow a complicated regular expression to be built up in steps from simpler parts, e.g.:

    const date = rx`\d{4}-\d{2}-\d{2}`
    const time = rx`\d{2}:\d{2}:\d{2}`
    const dateTime = rx`
      (${date})           // date
      T                   // time separator
      (${time})           // time
    `
    console.log(dateTime.exec(new Date().toISOString()))

Note that embedded sub-expressions are automatically surrounded with (?: and ), so that they are always treated as a self-contained unit. Also note that embedded sub-expressions will be run using the flags of the parent expression, regardless of what flags were on the sub-expression - so, for example, if the sub-expression had the 'case insensitive' flag set but the parent expression didn't, then the sub-expression will be executed in a case sensitive manner.

You can use regular expression flags by accessing them as a property of rx, e.g.:

    const alpha = rx.i`[a-z]+`
    const allAlpha = rx.gi`[a-z]+`

If you want to use a string that would otherwise be ignored (i.e. whitespace or //), you can simply escape it with backslashes or a character class:

    const url = rx.i`
      [ ]*([a-z]+):\/\/  // scheme
      ([^/]+)           // location
      (?:/(.*))         // path
    `

History

3.0.0 (2023-06-04)

• Allow embedding of other RegExp objects.

2.0.0 (2022-05-03)

• Use 'Proxy' objects to avoid having to create static properties for every permutation of the possible flags.

1.0.0 (2021-05-24)

• Initial release.