text: // 测试练习
  // 要求写出控制台的输出.
  
  function Parent() {
    this.a = 1;
    this.b = [1, 2, this.a];
    this.c = { demo: 5 };
    this.show = function () {
      console.log(this.a , this.b , this.c.demo );
    }
  }
  
  function Child() {
    this.a = 2;
    this.change = function () {
      this.b.push(this.a);
      this.a = this.b.length;
      this.c.demo = this.a++;
    }
  }
  
  Child.prototype = new Parent();
  
  var parent = new Parent();
  var child1 = new Child();
  var child2 = new Child();
  
  child1.a = 11;
  child2.a = 12;
  
  parent.show();
  child1.show();
  child2.show();
  
  child1.change();
  child2.change();
  parent.show();
  child1.show();
  child2.show();
  
  
  // https://blog.51cto.com/13869008/2152240
  