Important

This repository is moved to Codeberg.org.

For now it is kept in sync with the original repository @Github.

Depending on future USA/Microsoft/Github policies the Github version maybe discontinued later.

In other words, starting july 12 2025 the Codeberg repository is authorative.

RegexHelper

A module to create JS regular expressions with comments and whitespace using a tagged template

Demonstration/examples.

Import

import $RE from "[location of RegexpCreator.js]";

Syntax

const noCommentRE = $RE`
  // -------------------------------------------------------------------
  //  this regular expression finds all comment sections in a JS-string
  // -------------------------------------------------------------------
  \/\* ( ?: [^*] | \*+[^*\/] ) *\*+\/ // multiline (/* ... */)
  |                                   // or
  ( ?<!:|\\\|' ) \/\/.*               // single line (// ...)`;

// noCommentRE => /\/\*(?:[^*]|\*+[^*\/])*\*+\/|(?<!:|\\\|')\/\/.*/gm

const cleaned = "Hello world /* no comment */\nHello // no world"
  .replace(noCommentRE.flags(`g`), ``)

// cleaned => Hello world\nHello

escape

The imported function (here $RE) has a static escape method to escape strings for a regular expression.

It either uses the new (generally available) RegExp.escape or a proprietary escape method for older browsers.

  $RE.escape(`Hello (world)`); // result => 
  // using RegExp.escape: "\x48ello\x20\(world\\)"
  // using proprietary method: "\Hello\x20\(world\)";

flags

A $RE-instance is actually a Proxy. It can be used as a regular expression, but also contains a flags method and a getter (re) for the actual regular expression value.

The [$RE instance].re getter return the actual RegExp instance.

Flags can be added using the instance flags method [$RE RegEx instance].flags([flags:string]) or (legacy) by adding an Array of flag strings as last replacement in the template string e.g. $RE`[ABZ].+ ${["g", "u"]}` .

To remove all current flags, use [$RE RegEx instance].flags("-r").

The flags method is chainable. So [$RE RegEx instance].flags("-r").flags("gm") removes current flags from the instance and re-adds gm.

Replacing flags in the instance can be accomplished using the above mentioned (chaining) or [$RE RegEx instance].flags("-r|[new flags]") (so remove current flags -r, then add |[new flags], e.g. [$RE RegEx instance].flags(-r|iu).

Notes

• The replacement value must be the last replacement in the template string.
• The given flags are checked and cleaned

plain spaces

To insert a plain space (so not a whitespace) use <!32>

const hiRE = $RE`
    Hello<!32> /* <= this will be a plain space in the result */ {1,} 
    .*`.flags(`gi`);
// hiRE => /Hello {1,}.*/gi 
const hi = hiRE.test("hello    world!"); 
// hi => true

Or use $re.escape

const hiRE = $RE`
    Hello${$re.escape(` `)} /* <= this will be \x20 in the result */ {1,} 
    .*`.flags(`gi`);
// hiRE => /Hello\x20{1,}.*/gi

hiRE.test("hello    world!"); // => true