Equivalent of ASP's .Contains method

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.

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