javaScript中的继承

借用原型链通过prototype属性

function SuperType() {
  this.superType = 'SuperType';
}
SuperType.prototype.getSuper = function() {
  return this.superType;
}

function ChildType() {
  this.childType = ';childType'
}
// 继承了SuperType
ChildType.prototype = new SuperType(); 

let instance1 = new ChildType();

console.log(instance1.getSuper()); // 'SuperType'
//如果父类上也相同的方法或者属性，将会覆盖这个方法，但不影响父类方法或属性

借用构造函数 apply和call 优点可以传递参数

function SuperType() {
    this.colors = ['red', 'blue', 'green']
}

function SubType() {
    // 继承SuperType
    SuperType.call(this)
}

var instance1 = new SubType() var instance2 = new SubType()

instance1.colors.push('black') console.log(instance1.colors) // ["red", "blue", "green", "black"]
console.log(instance2.colors) // ["red", "blue", "green"]

组合继承原型链+构造函数

function SuperType(name) {
  this.name = name;
  this.colors = ['red', 'green', 'yellow'];
}
SuperType.prototype.getColors = function() {
  return this.colors;
}

function ChildType(name) {
  // 继承属性
  SuperType.call(this, name);
}
// 继承方法
ChildType.prototype = new SuperType();

let instance1 = new ChildType('Nick');
let instance2 = new ChildType('Cherry');
instance1.colors.push('black');

console.log(instance1.name); // 'Nick'
console.log(instance1.colors); // ' ["red", "green", "yellow", "black"]'
instance1.getColors(); // ' ["red", "green", "yellow", "black"]'
console.log(instance2.name); // 'Cherry'
console.log(instance2.colors); //  ["red", "green", "yellow"]

通过Object.create()与Object.defineProperties()方法的第二参数格式相同，

let person = {
  name: 'Nick',
  friends: ['cherry', 'july'],
};

let person1 = Object.create(person);
person1.name = 'Jhon';
person1.friends.push('cherry');

let person2 = Object.create(person);
person2.name = 'Lily';
person2.friends.push('Bob');

console.log(person.friends); // ["cherry", "july", "cherry", "Bob"]

var person = {
    name: "Bob",
    friends: ["Shelby", "Court", "Van"]
};

var anotherPerson = Object.create(person, {
    name: {
        value: "Greg"
    },
    age: {
        value: 18
    }
});

alert(anotherPerson.name);    //Greg
alert(anotherPerson.age);    //18
alert(person.name);        //Bob

寄生式继承创建一个仅用于封装继承过程的函数，该函数在内部以某种方式来增强对象，最后返回对象.

function createAnother(original){
    var clone = Object.create(original);    //通过调用函数创建一个新对象
    clone.sayHi = function(){               //以某种方式来增强这个对象
        alert("Hi");
    };
    
    return clone;                        //返回这个对象
}

var person = {
    name: "Bob",
    friends: ["Shelby", "Court", "Van"]
};
var anotherPerson = createAnother(person);
anotherPerson.sayHi();

寄生组合式继承都会调用两次构造函数：一次是在创建子类型原型时，另一次是在子类型构造函数内部。

function SuperType(name){
    this.name = name;
    this.colors = ["red", "blue", "green"];
}
SuperType.prototype.sayName = function(){
    alert(this.name);
}

function SubType(name, age){
    SuperType.call(this, name);　　//第二次调用SuperType()
    
    this.age = age;
}
SubType.prototype = new SuperType();　　//第一次调用SuperType()
SubType.prototype.sayAge = function(){
    alert(this.age);
}

function inheritPrototype(subType, superType){
    var protoType = Object.create(superType.prototype);    //创建对象
    protoType.constructor = subType;                    //增强对象
    subType.prototype = protoType;                        //指定对象
}
function SuperType(name){
    this.name = name;
    this.colors = ["red", "blue", "green"];
}
SuperType.prototype.sayName = function(){
    alert(this.name);
}

function SubType(name, age){
    SuperType.call(this, name);　　
    
    this.age = age;
}
inheritPrototype(SubType, SuperType)
SubType.prototype.sayAge = function(){
    alert(this.age);
}

var instance = new SubType("Bob", 18);
instance.sayName();
instance.sayAge();

inheritPrototype函数接收两个参数：子类型构造函数和超类型构造函数。
1. 创建超类型原型的副本。
2. 为创建的副本添加constructor属性，弥补因重写原型而失去的默认的constructor属性
3. 将新创建的对象（即副本）赋值给子类型的原型
这种方法只调用了一次SuperType构造函数，instanceof 和isPrototypeOf()也能正常使用。