rett

Regular Expressions Template Tag

Features

• Removes need to use double backslash.
• Escapes special regex characters.
• Choosing when to escape special characters.
• Multiline regex with comments and indents.
• Utility for making complex regex.

Usage

Basic Use

The re function can either take a template tag or be called normally.
When called normally, it takes regex flags and can only take a template tag from then on.

const re = require('rett');

console.log(re`\d+\b`);
// => /\d+\b/

console.log(re('gi')`\b[a-z]\b`);
// => /\b[a-z]\b/gi

Substitutions

Interpolate values just like any other template string.
All values will automatically be escaped.

const text = '?+{[()';

console.log(re`${text} \d+`);
// => /\?\+\{\[\(\) \d+/

Multiline Regex

The re.line function is used for multiline regex.
It has support for indents as well as single-line comments.
It works in the same way as the re function.

console.log(re.line`
    (
        \d+     // Digits
        [A-Z]   // Letter
    )
`);

// => /(\d+[A-Z])/

Ignoring Escape

Ignore escapes if you are planning on building regex bit by bit.
This is done with the re.ignore function which can take either a string or a template tag.
The re.raw function is also available for disabling escaping altogether.

const special = '{0,2}';

console.log(re`1${re.ignore(special)}`);
// => /1{0,2}/

console.log(re.raw`1${special}`);
// => /1{0,2}/

const digits = re.ignore`\d+`;

console.log(re`-?${digits}`);
// => /-?\d+/

Utility

re.escape()

Escapes special regex characters from a string.
Can take a template tag and will escape interpolated values.

console.log(re.escape('What?'));
// => 'What\\?'

re.unescape()

Unescapes special regex characters from a string.
Can take a template tag and will unescape interpolated values.
Note that this is not a perfect reversal.

console.log(re.unescape('What\\?'));
// => 'What?'

re.join()

Joins an array together by a character.
Escapes the values of the array.
Useful for making different possibilties with | in regex.

const list = re.join(['(', ')', '?']);
const regex = re`${list}`;

console.log(regex);
// => /\(|\)|\?/

Options

re.options

You can set the default options here.

• escape: default for escaping substitutions.
• multiline: default for parsing as multiline.
• debug: logs to console whenever a regex is made.
• flags.default: default for flags if no flags provided.
• flags.addtion: flags to add onto exisiting flags.

re.options = {
    escape: true,
    multiline: true,
    debug: true,
    flags: {
        default: 'u',
        addition: 'u'
    }
};

console.log(re`
    ABC  // Matches A, B, then C.
    (\d) // Then a number.
`);

// => /ABC(\d)/u

re.specialEscapeRegex

Regex for escaping special characters.
Reassign with your own if needed.

re.RegExp

Constructor used for creating new regular expression instances.
Reassign with your own if needed.

Other

re.create()

Creates a new regex from the values inputted.
Used internally.

console.log(re.create(['a', 'b'], [1], { flags: 'g' }));
// => /a1b/g

re.isTemplateTag()

Checks if a value is a template tag.
Used internally.

console.log(re.isTemplateTag`asdf`);
// => true