//我希望字符串中有一个倒序字符串的方法
    String.prototype.myReverse = function () {
      for (var i = this.length - 1; i >= 0; i--) {
        console.log(this[i]);
      }
    };
    var str = "abcdefg";
    str.myReverse();

    //为Array内置对象的原型对象中添加方法
    Array.prototype.mySort = function () {
      for (var i = 0; i < this.length - 1; i++) {
        for (var j = 0; j < this.length - 1 - i; j++) {
          if (this[j] < this[j + 1]) {
            var temp = this[j];
            this[j] = this[j + 1];
            this[j + 1] = temp;
          }//end if
        } //end for
      }//end for
    };

    var arr = [30, 19, 304, 83, 349, 98, 90];
    arr.mySort();
    console.log(arr);

    //为字符串内置对象的原型对象中添加了sayHi的方法
    String.prototype.sayHi = function () {
      console.log(this + "你好");
    };

    //字符串就有了打招呼的方法
    var str2 = "Node.js开发指南";
    str2.sayHi();