#正式發布的ES6中已經封裝實作了其他OO語言中的#繼承##形式,Class Extends#,這裡主要記錄js的原型繼承和借用建構子繼承
##一一、原型鏈繼承function Super(){
this.name="小明";
}
Super.prototype.sayName = function(){
alert(this.name)
};function Sub(){}
Sub.prototype = new Super();var instance = new Sub();
instance.sayName();//小明1234567891011
//當超類別中包含引用類型屬性值時,其中一個子類別的多個實例中,只要其中一個實例引用屬性只發生修改一個修改,其他實例的引用類型屬性值也會立即發生改變//原因是超類別的屬性變成子類別的原型屬性function Super(){this.name="小明"; this.friends = ['小紅','小強'];
}Super.prototype.sayName = function(){ alert(this.name) };function Sub(){} Sub.prototype = new Super();var instance1 = new Sub();var instance2 = new Sub(); instance1.friends.push('张三'); console.log(instance1.friends);//["小红", "小强", "张三"]console.log(instance2.friends);//["小红", "小强", "张三"]1234567891011121314151617
二、借用建構子繼承
function Super(){this.name="小明"; this.friends = ['小红','小强']; } Super.prototype.sayName = function(){ alert(this.name) };function Sub(){ Super.call(this); }var instance1 = new Sub();var instance2 = new Sub(); instance1.friends.push('张三'); console.log(instance1.friends);//["小红", "小强", "张三"]console.log(instance2.friends);//["小红", "小强"]12345678910111213141516
屬性與方法
function Super(){this.name="小明"; this.friends = ['小红','小强']; } Super.prototype.sayName = function(){ alert(this.name) };function Sub(){ Super.call(this); } Sub.prototype = new Super();var instance1 = new Sub();var instance2 = new Sub(); instance1.friends.push('张三'); console.log(instance1.friends);//["小红", "小强", "张三"]console.log(instance2.friends);//["小红", "小强"]instance1.sayName();//小明instance2.sayName();//小明12345678910111213141516171819
//组合式继承中,超类的构造函数将被调用两次function Super(){this.name="小明"; this.friends = ['小红','小强']; } Super.prototype.sayName = function(){ alert(this.name) };function Sub(){ Super.call(this);//第二次调用} Sub.prototype = new Super();//第一次调用var instance = new Sub();1234567891011121314
createAnother(original){ var clone = Object(original);//创建一个新对象,original的副本 clone.sayName = function(){ //对象的增强,添加额外的方法 alert('hi'); } return clone; }var person = { name:'小明', friends:['小红','小强'] }var person1 = createAnother(person);var person2 = createAnother(person); person1.friends.push('张三'); console.log(person.friends);//["小红", "小强", "张三"]console.log(person1.friends);//["小红", "小强", "张三"]console.log(person2.friends);//["小红", "小强", "张三"]123456789101112131415161718
//寄生组合式继承解决了组合式继承调用两次超类构造函数的问题function inheritPrototype(sub,superr){var prototype = Object.create(superr.prototype);//ES5中 创建对象 副本的方法 prototype.constructor = superr; //弥补重写原型失去的默认constructor属性 sub.prototype = prototype; }function Super(name){ this.name = name; this.friends = ['小红','小强']; } Super.prototype.sayName = function(){ alert(this.name); }function Sub(name){ Super.call(this,name); } inheritPrototype(Sub,Super);var person1 = new Sub('小明');var person2 = new Sub('小华'); person1.friends.push('张三'); console.log(person1.friends);//["小红", "小强", "张三"]console.log(person2.friends);//["小红", "小强"]console.log(person1.sayName());//小明console.log(person2.sayName());//小华
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