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