JS设计模式 -- 4种创建型模式

1. 工厂模式

作用：实现对象的批量创建

/* 构造函数 */
function Person(name) {
  this.name = name;
}
function Car(model) {
  this.model = model;
}
/* 创建 */
function create(type, val) {
  return (this instanceof create) ?
    this[type](val) : new create(type, val);
}
create.prototype = {
  person: Person,
  car: Car
}
console.log(create('person', 'zhangsan'))
console.log(new create('car', 'bwm'))

2. 原型模式

作用：创建一个共享原型，通过拷贝这个原型来创建新的类

// 也可以是其他类的原型
let prototype = {
  say() {
    console.log(this.name);
  }
}
function Person() {
  function F() { };
  F.prototype = prototype;
  let f = new F();
  f.name = "zhansan";
  return f;
}
new Person().say();// zhansan

3. 建造者模式

作用：将创建对象的细节分为创建子对象的过程，使结构更加清晰

/* 实现 */
function Person(name) {
  this.name = name;
}

function CreateName(name) {
  this.wholeName = name;
  [this.firstName, this.lastName] = name.split(' ');
}

function CreateWork(workName) {
  switch (workName) {
    case 'engineer':
      this.workName = "工程师";
      this.desc = "热爱编程";
      break;
    case 'teacher':
      this.workName = "老师";
      this.desc = "热爱分享";
      break;
    default:
      this.workName = workName;
      this.desc = "无";
  }
}
CreateWork.prototype.changeWork = function (workName, desc) {
  workName && (this.workName = workName);
  desc && (this.desc = desc);
}
/* 创建类 */
function Candidate(params) {
  let _candidate = new Person();
  _candidate.name = new CreateName(params.name);
  _candidate.work = new CreateWork(params.work);
  return _candidate;
}

/* 举例 */
let arr = [
  { name: "zhang san", work: "engineer" },
  { name: "li si", work: "teacher" }
];
let candidates = [];
arr.forEach(v => {
  candidates.push(new Candidate(v));
})
console.log(candidates[0]);
candidates[0].work.changeWork('学生', '热爱学习');
console.log(candidates[0]);

4. 单例模式

作用：实现无论创建多少个对象都返回同一个

const createSingle = (function () {
  let _unique = null;// 私有变量
  return function () {
    if (_unique === null) {
      _unique = { a: 1 };
    }
    return _unique;
  }
})();

let single1 = createSingle();
let single2 = createSingle();
console.log(single1 === single2);// true