16. Inheritance

Prototypal Inheritance

Object.create(obj) 以obj为原型创造实例

let person = {
  name: "Nicholas",
  friends: ["Shelby", "Court", "Van"]
};
let anotherPerson = Object.create(person);
anotherPerson.name = "Greg";
anotherPerson.friends.push("Rob");
let yetAnotherPerson = Object.create(person);
yetAnotherPerson.name = "Linda";
yetAnotherPerson.friends.push("Barbie");
console.log(person.friends); // "Shelby,Court,Van,Rob,Barbie"

Object.create()可以传第二个参数，和Object.defineProperties()一样，给实例添加属性

let person = {
  name: "Nicholas",
  friends: ["Shelby", "Court", "Van"]
};
let anotherPerson = Object.create(person, {
    name: {
    value: "Greg"
    }
});
console.log(anotherPerson.name); // "Greg"

Parasitic(寄生) Inheritance

用一个函数返回一个对象

function createAnother(original){
  let clone = object(original); // create a new object by calling a function
  clone.sayHi = function() { // augment the object in some way
    console.log("hi");
  };
  return clone; // return the object
}
let person = {
  name: "Nicholas",
  friends: ["Shelby", "Court", "Van"]
};
let anotherPerson = createAnother(person);
anotherPerson.sayHi(); // "hi"

寄生式组合继承

function inheritPrototype(subType, superType) {
  let prototype = object(superType.prototype);
  // 创建父类原型的一个副本
  prototype.constructor = subType;
  // 增强对象
  subType.prototype = prototype;
  // 赋值对象
}
function SuperType(name) {
  this.name = name;
  this.colors = ["red", "blue", "green"];
}
SuperType.prototype.sayName = function() {
    console.log(this.name);
};
function SubType(name, age) {
  SuperType.call(this, name);
  this.age = age;
}
inheritPrototype(SubType, SuperType);
SubType.prototype.sayAge = function() {
  console.log(this.age);
};