// 组合方式
function Parent3 () {
this.name = 'Parent3';
this.play = [1, 2, 3];
}
function Child3 () {
Parent3.call(this); // 父级的构造函数执行了两次
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; // 引用类型
var s5 = new Child4();
var s6 = new Child4();
s5.play.push(4);
console.log(s5, s6);
console.log (s5 instanceof Parent4);
console.log (s5 instanceof Child4);
// 如何判断s5是child4的实例还是parent4的实例
console.log (s5.constructor)
// 从父类的原型链中继承了constructor
// 组合继承优化2
function Parent5 () {
this.name = 'Parent5';
this.play = [1, 2, 3];
}
function Child5 () {
Parent4.call(this);
this.type = 'child5';
}
Child5.prototype = Object.create(Parent5.prototype); // 引用类型 父子原型链隔离
Child5.prototype.constructor = Child5; // 重写child5的构造函数
var s7 = new Child5();
var s8 = new Child5();
s7.play.push(4);
console.log(s7, s8);
console.log (s7.constructor);
</script>
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