In JavaScript, regular expressions, often abbreviated regex or regexp, are patterns used to match, validate, extract, and replace character combinations in strings.

Creating a regular expression

To create a new regular expression object, you can write a regex literal using the double slash syntax //:

const regex = /pattern/;

Where pattern is a string or regular expression.

Matching patterns in strings

Checking if a pattern exists

To check whether a pattern exists in a string, you can use the test() method of the regex object:

let exists = /pattern/.test(string);

Where:

• /pattern/ is a regular expression.
• string is a string of characters.

This function returns true if the pattern exists, and false otherwise.

Listing all matching patterns

To list all the matched occurrences of the pattern in a string, you can use the match() method of the string: