Equivalent of ASP's .Contains method [duplicate]

Possible Duplicate:
JavaScript: string contains
Jquery: How to see if string contains substring

In ASP .NET C# I use:

string aa = "aa bb";
if (aa.Contains("aa"))
   { 
       //Some task       
   }

I want to same thing in client side means in JQuery. Something like below:

var aa = "aa bb";
if(aa. -----want help here){
}

Is there any method to do this?

Use the String.indexOf() ^{MDN Docs} method

if( aa.indexOf('aa') != -1 ){
// do whatever
}

Update

Since ES6, there is a String.includes() ^{MDN Docs} so you can do

if( aa.includes('aa') ){
// do whatever
}

You don't need jQuery for this. It can be achieved with simple pure JavaScript:

var aa = "aa bb";
if(aa.indexOf("aa") >= 0){
   //some task
}

The method indexOf will return the first index of the given substring in the string, or -1 if such substring does not exist.

C#'s implementation of .Contains is actually a wrapper on it's implementation of .IndexOf. Therefore you can create your own .Contains function in javascript like this:

String.prototype.Contains = function (s) {
    return this.indexOf(s) != -1;
}