Regular expressions are character sequences to test for matching patterns in strings. The RegEx sequence is placed between two forward slashes. You can store a RegEx in a variable or use a RegEx object. Example using the test() method on a RegEx object.

> /o/.test('bobcat')
= true

> /l/.test('bobcat')
= false

The RegEx match() method returns an array with all matches, or null if there is no match.

The /g flag signifies a global match so the returned array includes all matching substrings.