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js继承如何实现的

2026-04-04 01:27:19JavaScript

原型链继承

通过让子类的原型对象指向父类的实例来实现继承。子类实例通过原型链访问父类的属性和方法。

function Parent() {
  this.name = 'parent';
}
Parent.prototype.sayName = function() {
  console.log(this.name);
};

function Child() {}
Child.prototype = new Parent();

const child = new Child();
child.sayName(); // 'parent'

构造函数继承

在子类构造函数中调用父类构造函数，使用call或apply方法改变this指向。

function Parent(name) {
  this.name = name;
}

function Child(name) {
  Parent.call(this, name);
}

const child = new Child('child');
console.log(child.name); // 'child'

组合继承

结合原型链继承和构造函数继承，既继承原型方法又保证实例属性独立。

function Parent(name) {
  this.name = name;
}
Parent.prototype.sayName = function() {
  console.log(this.name);
};

function Child(name, age) {
  Parent.call(this, name);
  this.age = age;
}
Child.prototype = new Parent();
Child.prototype.constructor = Child;

const child = new Child('child', 10);
child.sayName(); // 'child'

原型式继承

基于已有对象创建新对象，无需明确定义构造函数。

const parent = {
  name: 'parent',
  sayName: function() {
    console.log(this.name);
  }
};

const child = Object.create(parent);
child.name = 'child';
child.sayName(); // 'child'

寄生式继承

在原型式继承基础上增强对象，添加额外方法。

function createAnother(original) {
  const clone = Object.create(original);
  clone.sayHi = function() {
    console.log('hi');
  };
  return clone;
}

const parent = {
  name: 'parent'
};
const child = createAnother(parent);
child.sayHi(); // 'hi'

寄生组合式继承

目前最理想的继承方式，通过借用构造函数继承属性，通过原型链混成形式继承方法。

function inheritPrototype(child, parent) {
  const prototype = Object.create(parent.prototype);
  prototype.constructor = child;
  child.prototype = prototype;
}

function Parent(name) {
  this.name = name;
}
Parent.prototype.sayName = function() {
  console.log(this.name);
};

function Child(name, age) {
  Parent.call(this, name);
  this.age = age;
}
inheritPrototype(Child, Parent);

const child = new Child('child', 10);
child.sayName(); // 'child'

ES6类继承

使用class和extends语法糖实现继承，底层仍是原型继承。

js继承如何实现的

class Parent {
  constructor(name) {
    this.name = name;
  }
  sayName() {
    console.log(this.name);
  }
}

class Child extends Parent {
  constructor(name, age) {
    super(name);
    this.age = age;
  }
}

const child = new Child('child', 10);
child.sayName(); // 'child'