Showing posts with label JavaScript RegExp Object. Show all posts
Showing posts with label JavaScript RegExp Object. Show all posts

Wednesday, August 29, 2012

JavaScript RegExp Object


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

var patt=new RegExp(pattern,modifiers);

or more simply:

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:
var str="Visit W3Schools";
var patt1=/w3schools/i;
The marked text below shows where the expression gets a match:
Visit W3Schools

Try it yourself »

Example 2

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

Try it yourself »

Example 3

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

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:
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

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:
e

Try it yourself »