Array.prototype.min = function(comparer) {

​

    if (this.length === 0) return null;

    if (this.length === 1) return this[0];

​

    comparer = (comparer || Math.min);

​

    var v = this[0];

    for (var i = 1; i < this.length; i++)

        v = comparer(this[i], v);    

​

    return v;

}

​

Array.prototype.max = function(comparer) {

​

    if (this.length === 0) return null;

    if (this.length === 1) return this[0];

​

    comparer = (comparer || Math.max);

​

    var v = this[0];

    for (var i = 1; i < this.length; i++)

        v = comparer(this[i], v);    

​

    return v;

}

​

var ar = new Array(1,4,8,7,5,9,6,10,15,20,45,65,78,3);

​

alert(ar.max());