javascript - Jquery, checking if a value exists in array or not

I believe this question will be fairly easy for the ones who played around with java script / jquery.

var arr = new Array();

$.map(arr, function() {
 if (this.id == productID) {
   this.price = productPrice;
 }else {
  arr.push({id: productID, price: productPrice})
 }
}

I guess the code above explains what I want in really simple way. I would imagine this $.map would work like this but unfortunately I couldn't get results with this.

What is the most simple and elegant way to do this? Do I truly go through all array just to find if a key's value is there or not?

Does Jquery has something like isset($array['key'])?

EDIT

I tried to use inArray but it keeps adding object to array even if there is a match.

if ( $.inArray(productID, arr) > -1) {
   var number = $.inArray(productID, arr);
   orderInfo[number].price = parseFloat(productPrice);
}else {
   orderInfo.push({id:productID, price:parseFloat(productPrice)});
}

Answer

If you want to do it using .map() or just want to know how it works you can do it like this:

var added=false;
$.map(arr, function(elementOfArray, indexInArray) {
 if (elementOfArray.id == productID) {
   elementOfArray.price = productPrice;
   added = true;
 }
}
if (!added) {

  arr.push({id: productID, price: productPrice})
}

The function handles each element separately. The .inArray() proposed in other answers is probably the more efficient way to do it.