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JavaScript中的继承
一、原型链(默认)
function Person(){};
function Student(){};
Student.prototype = new Person();
Student.prototype.constructor = Student;
缺点:1、传参怎么搞 ? 2、new Person的实例属性成了Student的原型属性
二、借用构造函数
function Person(name) { this.name = name;}
function Student(name, klass) { Person.call(this, name); this.klass = klass;}
优点:传参搞定了哦 缺点:方法继承呢 继承 呢
三、组合继承(原型链+借用构造函数)
1 function Person(name){ 2 this.name = name; 3 } 4 5 function Student(name, klass){ 6 Person.call(this, name); 7 this.klass = klass; 8 } 9 10 Student.prototype = new Person(); 11 Student.prototype.constructor = Student;
还存在缺点:1、new Person的实例属性成了Student的原型属性 2 Person构造函数被调用了两次,效率低下
四、临时构造函数
1 function Person(name){ 2 this.name = name; 3 } 4 5 function Student(name, klass){ 6 Person.call(this, name); 7 this.klass = klass; 8 } 9 10 (function(){ 11 var F = function(){}; 12 F.prototype = Person.prototype; 13 Student.prototype = new F(); 14 Student.prototype.constructor = Student; 15 })();
看起来不错哦~~
但素,JavaScript为啥非得类式继承捏
重点来了,
原型继承
Student.prototype = Object.create(Person.prototype);
Student.prototype.constructor = Student;
原型链,链起来:new student() -----> Student.prototype----->Person.prototype-----> Object.Prototype
把你的心,我的心,串一串,串一株幸运草,串一个同心圆~~
Object.create polyfill
if(typeof Object.create !== ‘function‘){ Object.create = function(o){ var F = function(){}; F.prototype = o; return new F(); } }
额外的,通过复制属性实现继承
1 function extendDeep(parent, child){ 2 var i; 3 child = child || {}; 4 for(i in parent){ 5 if(parent.hasOwnProperty(i)){ 6 if(typeof parent[i] === ‘object‘){ 7 child[i] = (Object.prototype.toString.call(parent[i]) === ‘[object Array]‘) ? [] : {}; 8 extendDeep(parent[i], child[i]); 9 }else{ 10 child[i] = parent[i]; 11 } 12 } 13 } 14 return child; 15 }
JavaScript中的继承