实现继承的方式

/*** 借助构造函数实现继承*/function Parent1(){this.name = "parent1";}Parent1.prototype.say = function(){};function Child1(){//将父构造函数的this指向子构造函数的实例上Parent1.call(this);//applythis.type = "child1";}console.log(new Child1);/*** 借助原型链实现继承*/function Parent2(){this.name = 'parent2';this.play = [1,2,3];}function Child2(){this.type = 'child2';}Child2.prototype = new Parent2();console.log(new Child2);var s1 = new Child2();var s2 = new Child2();console.log(s1.play,s2.play);s1.play.push(4);/*** 组合方式* 缺点民：实例化两次父类*/function Parent3(){this.name = "parent3";this.play = [1,2,3];}function Child3(){Parent3.call(this);this.type = 'child3';}Child3.prototype = new Parent3();var s3 = new Child3();var s4 = new Child3();s3.play.push(4);console.log(s3.play, s4.play);/*** 组合继承的优化1*/function Parent4(){this.name = "parent4";this.play = [1,2,3];}function Child4(){Parent4.call(this);this.type = 'child4';}Child4.prototype = Parent4.prototype;var s5 = new Child4();var s6 = new Child4();console.log(s5, s6);console.log(s5 instanceof Child4,s5 instanceof Parent4);//构造函数是一个，无法判断实例是父类创建还是子类创建
    console.log(s5.constructor);/*** 组合继承优化2*/function Parent5(){this.name = "parent5";this.play = [1,2,3];}function Child5(){Parent5.call(this);this.type = 'child5';}//创建中间对象Child5.prototype = Object.create(Parent5.prototype);Child5.prototype.constructor = Child5;var s7 = new Child5();console.log(s7 instanceof Child5, s7 instanceof Parent5);console.log(s7.constructor);

//模拟new func就是一个构造函数var new2 = function(func){//第一步，创建一个空对象，空对象关联构造函数的原型对象var o = Object.create(func.prototype);//第二步，执行构造函数，k表示返回结果var k = func.call(o);//第三步，判断构造函数的动行结果是不是对象类型if(typeof k === 'object'){return k;}else{return o;}}