Javascript Array move(pos1, pos2)

Array.prototype.move = function (pos1, pos2) {
    // local variables
    var i, tmp;/*from www. j a v  a  2  s . c o  m*/
    // cast input parameters to integers
    pos1 = parseInt(pos1, 10);
    pos2 = parseInt(pos2, 10);
    // if positions are different and inside array
    if (pos1 !== pos2 &&
        0 <= pos1 && pos1 <= this.length &&
        0 <= pos2 && pos2 <= this.length) {
        // save element from position 1
        tmp = this[pos1];
        // move element down and shift other elements up
        if (pos1 < pos2) {
            for (i = pos1; i < pos2; i++) {
                this[i] = this[i + 1];
            }
        }
        // move element up and shift other elements down
        else {
            for (i = pos1; i > pos2; i--) {
                this[i] = this[i - 1];
            }
        }
        // put element from position 1 to destination
        this[pos2] = tmp;
    }
}