🍦 JavaScript -

Regex

There are two ways to create regular expression variable. Prefer shorter syntax / / if possible.

var rule = new RegExp('test');
var rule = /test/;

Basic regular expression syntax.

var rule = /[pb]attern/;   // match in set
var rule = /[^acd]attern/  // match not in set
var rule = /pa[t]{2}rn/    // count
var rule = /pattern?/      // 0 or 1
var rule = /pattern*/      // 0 or more
var rule = /pattern+/      // 1 or more

var rule = /pattern/i   // incase-sensitive matching
var rule = /pattern/g   // match all, not just first
var rule = /pattern/m   // multiline

Check for matches in a string.

var rule = /test/;
rule.test('Is this a test?');
// => true

Split using regex.

var rule = /test/;
'Is this a test or not a test?'.split(rule);
// => ['Is this a ', ' or not a ', '?']

Replace first that regex matches.

var rule = /test/;
'Is this a test or not a test?'.replace(rule, 'hoot');
// => 'Is this a hoot or not a test?'

Replace all that regex matches.

var rule = /test/g;
'Is this a test or not a test?'.replace(rule, 'hoot');
// => 'Is this a hoot or not a hoot?'