JavaScript RegExp

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 txt=new RegExp(pattern,modifiers);

or more simply:

var txt=/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).

var str="Visit Hiscript";

var patt1=/Hiscript/i;

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":

var patt1=new RegExp("e");

document.write(patt1.test("The best things in life are free"));

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":

var patt1=new RegExp("e");

document.write(patt1.exec("The best things in life are free"));