Simple and Useful JavaScript Regular Expression Tutorial

Introduction

Regular Expression is a very important part of any language programming
because of its ability to help programmers to write fast and pure
applications.

You Don't Know What a Regular Expression Is?

A regular expression is an object that describes a pattern of characters.

Regular expressions are used to perform pattern-matching and
"search-and-replace" functions on text.

Web developer can also use Regular Expression in JavaScript. Now I describe
some simple examples of using Regular Expression in JavaScript.

The overall syntax should look like:

/pattern/modifiers

pattern specifies the search pattern
modifiers specify if our search should be case-sensitive, global, etc.
Modifiers Table

Modifier Description
i Perform case-insensitive matching
g Perform a global match (find all matches rather than stopping after the
first match)
m Perform multiline matching
To compile and use Regular Expression, you can use three useful functions.

Regular Expression Object Methods

Method Description
compile() Compiles a regular expression
exec() Tests for a match in a string. Returns the first match
test() Tests for a match in a string. Returns true or false
Example

Test sentence: Sometext sometext sometext

Expression Test Result
/sometext/ Sometext sometext sometext
/sometext/i Sometext sometext sometext
/sometext/g Sometext sometext sometext
/sometext/gi Sometext sometext sometext
/some/ Sometext sometext sometext
/some/i Sometext sometext sometext
/some/g Sometext sometext sometext
/some/ig Sometext sometext sometext