Javascript: Determine whether an array contains a value

Question

i need to determine if a value exists in an array using javascript.

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"));

Please suggest what to do

Answer 1

arrValues.indexOf('Sam') > -1

Apparently IE still doesn't have the Array.prototype.indexOf method. For IE,

if(!Array.prototype.indexOf) {
    Array.prototype.indexOf = function(needle) {
        for(var i = 0; i < this.length; i++) {
            if(this[i] === needle) {
                return i;
            }
        }
        return -1;
    };
}

Answer 2

This is generally what the indexOf() method is for. You would say:

if (arrValues.indexOf('Sam') > -1) {return true;}
else {return false;}

Answer 3

The code works in Safari 4.0.2.

BTW: I'd do a === comparison instead of just ==.

Answer 4

The above function always returns false.

No it doesn't: The function works as expected - the error must be somewhere else.

Answer 5

Given the implementation og indexOf for IE (as described by eyelidlessness):

Array.prototype.contains = function(obj) {
    return this.indexOf(obj) > -1;
};

Answer 6

jQuery has a utility function for this:

$.inArray(value, array)

Returns index of value in array. Returns -1 if array does not contain value.