1、混合继承的弊端
混合继承在继承原型的时候,其实将 父类的模板 再次继承,影响效率
// 混合继承 function Person(name,age) { this.name = name; this.age = age; } Person.prototype = { constructor : Person, sayHello : function () { alert("hello"); } } function Boy(name,age,sex) { //Person.call(this,name,age); this.sex = sex; } Boy.prototype = new Person(); // 虽然 在 new Person 的时候,并没有传入参数,但是 还是实例化了 Person 模板 , 只是参数的值默认为 undefined var b = new Boy("z3",25,"男"); alert(b.name); // undefined alert(b.sex); // 男
改进方法
// 改进方法 , 模拟 extjs 底层继承实现方式 function Person(name,age) { this.name = name; this.age = age; } Person.prototype = { constructor : Person, sayHello : function () { alert("hello"); } } function Boy(name,age,sex) { Boy.superClass.constructor.call(this,name,age); this.sex = sex; } function extend(sub,sup) { var F = new Function(); F.prototype = sup.prototype; sub.prototype = new F(); sub.prototype.constructor = sub; sub.superClass = sup.prototype; if(sup.prototype.constructor = Object.prototype.constructor){ sup.prototype.constructor = sup; } } extend(Boy,Person); var b = new Boy("z3",25,"男"); alert(b.name); // z3
时间: 2024-10-02 03:08:04