JavaScript Regular Expressions

JavaScript Regular Expressions

A Regular Expression (RegEx) is an object that describes a sequence of characters used defining a search pattern. 

Creating a Regular Expression

You construct a Regular Expression in one of two ways:

• Using a regular expression literal, which consists of a pattern enclose between slashes, as follows:

const re = /ab+c/;

Regular expression literals provide compilation of the regular expression when the script is loaded. If the regular expression remains constant, using this can improve performance.

• Or calling the constructor function of the RegExp object, as follows :

Const re = new RegExp(‘ab+c’);

Regular Expression Cheat Sheet

Example 1 – Do a case-insensitive search for “webdesigninghouse” in a string:

Output - 

Example2 – Do a global search for “e” in a string:

Output -

Example 3 - Calling the constructor function of the RegExp object, as follows:

 

Output -

Before clicking the button:

After clicking the button: