RegExp, is short for regular expression.

Complete RegExp Object Reference

For a complete reference of all the properties and methods that can be used with the RegExp object, go to our complete RegExp object reference.

The reference contains a brief description and examples of use for each property and method!


What is RegExp?

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

When you search in a text, you can use a pattern to describe what you are searching for.

A simple pattern can be one single character.

A more complicated pattern can consist of more characters, and can be used for parsing, format checking, substitution and more.

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

Syntax
Code:
var patt=new RegExp(pattern,modifiers);
or more simply:
Code:
var patt=/pattern/modifiers;
  • pattern specifies the pattern of an expression
  • modifiers specify if a search should be global, case-sensitive, etc.


RegExp Modifiers


Modifiers are used to perform case-insensitive and global searches.

The i modifier is used to perform case-insensitive matching.

The g modifier is used to perform a global match (find all matches rather than stopping after the first match).

Example 1

Do a case-insensitive search for "w3schools" in a string:
Code:
var str="Visit W3Schools";
var patt1=/w3schools/i;
The marked text below shows where the expression gets a match:
Code:
Visit W3Schools
Try it yourself »


Example 2

Do a global search for "is":
Code:
var str="Is this all there is?";
var patt1=/is/g;
The marked text below shows where the expression gets a match:
Code:
Is this all there is?
Try it yourself »


Example 3

Do a global, case-insensitive search for "is":
Code:
var str="Is this all there is?";
var patt1=/is/gi;
The marked text below shows where the expression gets a match:
Code:
Is this all there is?
Try it yourself »


test()

The test() method searches a string for a specified value, and returns true or false, depending on the result.

The following example searches a string for the character "e":

Example
Code:
var patt1=new RegExp("e");
document.write(patt1.test("The best things in life are free"));
Since there is an "e" in the string, the output of the code above will be:
Code:
true
Try it yourself »


exec()

The exec() method searches a string for a specified value, and returns the text of the found value. If no match is found, it returns null.

The following example searches a string for the character "e":

Example 1
Code:
var patt1=new RegExp("e");
document.write(patt1.exec("The best things in life are free"));
Since there is an "e" in the string, the output of the code above will be:
Code:
e
Try it yourself »