类与实例
类的声明
var Animal = function () {
this.name = 'Animal';
};
/**
* es6中class的声明
*/
class Animal2 {
constructor () {
this.name = 'Animal2';
}
}
实例化
console.log(new Animal(), new Animal2());
类的继承
借助构造函数实现继承
缺点:无法继承父类原型对象上的方法,实现了部分继承;但如果父类的属性在构造函数中可以实现继承。
function Parent1 () {
this.name = 'parent1';
}
Parent1.prototype.say = function () {
};
function Child1 () {
Parent1.call(this);
this.type = 'child1';
}
console.log(new Child1(), new Child1().say());
借助原型链实现继承
缺点:由于原型链中的原型对象是共享的,所以在一个实例更改其属性值时,另外一个实例所对应的属性值也会更改。
function Parent2 () {
this.name = 'parent2';
this.play = [1, 2, 3];
}
function Child2 () {
this.type = 'child2';
}
Child2.prototype = new Parent2();
var s1 = new Child2();
var s2 = new Child2();
console.log(s1.play, s2.play);
s1.play.push(4);
组合方式
缺点:父级的构造函数执行了两次
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);
console.log(s5.constructor);
组合继承的优化2
function Parent5 () {
this.name = 'parent5';
this.play = [1, 2, 3];
}
function Child5 () {
Parent5.call(this);
this.type = 'child5';
}
Child5.prototype = Object.create(Parent5.prototype);
相关学习文章链接:
JS中原型对象的彻底理解:https://blog.csdn.net/u012468376/article/details/53121081
JS原型彻底理解2—继承中的原型链:https://blog.csdn.net/u012468376/article/details/53127929
(本文纯属个人学习笔记,如有不足请留言!)