Get unique values of an Array

array.unique.js

Array.prototype.unique = function() {

    var unique = {}, // Object to keep track of unique occurrences
        ret = [], // Our return array, with unique values
        i, l; // iterator vars

    for (i = 0, l = this.length; i < l; i+=1) {

        // if the unique object already has the current array value,
        // skip to the next value of the array
        if (unique.hasOwnProperty(this[i])) {
            continue;
        }

        // if we make it this far, the value is unique. Push it
        // to the return array.
        ret.push(this[i]);

        // Once we have this value, make sure the unique object
        // knows it's already there.
        unique[this[i]] = 1;
    }

    return ret;

}