- 单例设计模式的核心
确保只有一个实例，供全局访问使用 - 普通对象
let F= function (name) {
this.name = name;
};
let a = new F("a");
let b = new F("b");
console.log(a===b); //false
不足之处：
（1）没有封装性，属性和方法都是暴露在外面的
（2）全局变量容易造成命名空间的污染
（3）容易造成对象的浪费
- 传统的单例
let Singleton = function (name) {
this.name = name;
this.instance = null;
};
Singleton.getInstance = function (name) {
if(!this.instance){
this.instance = new Singleton(name);
}
return this.instance;
};
let c= Singleton.getInstance("c");
let d= Singleton.getInstance("d");
console.log(c===d); //true
- 用代理实现单例设计模式
let createSingleton = function (name) {
this.name = name;
this.say();
};
createSingleton.prototype.say = function () {
console.log(this.name);
};
let ProxySingletonCreate = (function () {
let instance = null;
return function (name) {
if(!instance) {
instance = new createSingleton(name);
}
return instance;
}
})();
let e = new ProxySingletonCreate("e");
let f = new ProxySingletonCreate("f");
console.log(e===f); //true
console.log(e); //createSingleton { name: 'e' }
console.log(f); //createSingleton { name: 'e' }
