javascript - Determine whether an array contains a value

I need to determine if a value exists in an
array.

I am using the following
function:

Array.prototype.contains
            = function(obj) {
 var i = this.length;
 while (i--) {
 if
            (this[i] == obj) {
 return true;
 }
 }
 return
            false;
}

The
above function always returns false.

The array
values and the function call is as
below:

arrValues = ["Sam","Great",
            "Sample",
            "High"]
alert(arrValues.contains("Sam"));

Answer

var contains = function(needle)
            {
 // Per spec, the way to identify NaN is that it is not equal to
            itself
 var findNaN = needle !== needle;
 var
            indexOf;

 if(!findNaN && typeof Array.prototype.indexOf ===
            'function') {
 indexOf = Array.prototype.indexOf;
 } else
            {
 indexOf = function(needle) {
 var i = -1, index =
            -1;

 for(i = 0; i < this.length; i++) {
 var item =
            this[i];

 if((findNaN && item !== item) || item === needle)
            {
 index = i;
 break;
 }

            }

 return index;
 };
 }


            return indexOf.call(this, needle) >
            -1;
};

You
can use it like this:

var myArray
            = [0,1,2],
 needle = 1,
 index = contains.call(myArray, needle); //
            true

href="http://codepen.io/anon/pen/mVRNaJ" rel="noreferrer">CodePen
validation/usage