//最小值
Array.prototype.min = function() {
    var min = this[0];
    var len = this.length;
    for (var i = 1; i < len; i++){
       if (this[i] < min){
           min = this[i];
       }
    }
    return min;
}
//最大值
Array.prototype.max = function() {
    var max = this[0];
    var len = this.length;
    for (var i = 1; i < len; i++){
       if (this[i] > max) {
           max = this[i];
       }
    }
    return max;
}