heregex

ES6 tagged template to make regular expressions more easily readable.

Add comments using the # character prefixed with a space. All whitespace gets removed (so use \s for actual whitespace matching). Any flags go in ${'gim'} at the end of the string.

Examples

heregex = require('heregex')

let regex_github_repo = heregex`
  ^                    # start of string
  (?:https?:\/\/)?     # optional http/https
  (?:www\.)?           # optional "www."
  github\.com          # website address
  \/
  ([a-z0-9_-]+)        # username ($1)
  \/
  ([a-z0-9_-]+)        # repo ($2)
  (?:\.git)?           # optional .git
  ${'i'}
`;

Which creates this end result:

/^(?:https?:\/\/)?(?:www\.)?github\.com\/([a-z0-9_-]+)\/([a-z0-9_-]+)(?:\.git)?/i

The end result of that example is still readable, but if you're doing even slightly more complex regular expressions, multiple lines with comments becomes a lot easier to read:

heregex = require('heregex')

let regex_number = heregex`
    ^0b[01]+                   # binary
  | ^0o[0-7]+                  # octal
  | ^0x[0-9a-f]+               # hex
  | ^\d*\.?\d+ (?:e[+-]?\d+)?  # decimal
  ${'i'}
`;

which compiles down to the harder to read version:

/^0b[01]+|^0o[0-7]+|^0x[0-9a-f]+|^\d*\.?\d+(?:e[+-]?\d+)?/i

Installation

npm install --save heregex

or

yarn add heregex

If you'd like to use it without requiring it everywhere, you can add it to the list of node globals:

global.heregex = require('heregex');

Questions

How do I make a literal #?

Get rid of any whitespace immediately preceding it. For heregex to consider something a comment, it must have a space before the # or be the first character on a new line. If you need the space or if its the first character on a new line, escape it to \#. \# gets passed through directly as \#. This is not an issue, since an escaped # is still #.

let regex_basic_css_selector = heregex`
    ^\.([_a-z][_a-z0-9-]*)   # classname
  | ^#([_a-z][_a-z0-9-]*)    # id
  | ^([a-z0-9]+)             # type
  ${'i'}
`;

which evaluates to:

/^\.([_a-z][_a-z0-9-]*)|^#([_a-z][_a-z0-9-]*)|^([a-z0-9]+)/i