How to Use regex in Javascript

Learn how to use regex in javascript with examples.

What is RegEx

It is a built-in object, used to define a search pattern (or regular expression), which can be used to make a wide variety of tests on a given string. RegEx is also called a regular expression. There are two different ways in which we can define/create regular expressions in javascript:

1. Using RegExp object constructor notation
2. RegExp literal notation.

Using RegExp object constructor notation

Syntax:

var variablename = new RegExp("search pattern", ['"flags"]);

Ex: phone number validation:

var pattern = new RegExp["^[0-9]{10}$");

Using RegExp literal noatioan:

Syntax:

var variablename =/search pattern/[flags];

Ex: phone number validation:

var pattern = /^[0-9]{10}$/;

Basic Methods

test() Method: It is used to test if is there a match or no match between a regular expression and the given string. If there is a match then it returns true otherwise returns false.
syntax:

pattern.test(str:String):Boolean

Ex:

var ph = "1234567890";
var pattern =/^[0-9]{10}$/;

document.write(pattern.test(ph)); //true

Application of RegExp

1. Search for a word in a given string
2. Find & replace a word in a string
3. perform data validations, etc.