单例模式
箭头函数写法
const singleton = function () { };
singleton.getInstance = (() => {
let instance = null;
return () => {
if (!instance) {
instance = new singleton();
}
return instance;
}
})()
const s1 = singleton.getInstance();
const s2 = singleton.getInstance();
console.log(s1 === s2);//truefunction写法
singleton.getInstance=(function(){
let instance = null;
return function(){
if(!instance){
instance = new singleton();
}
return instance;
}
})();
const s1 = singleton.getInstance();
const s2 = singleton.getInstance();
console.log(s1===s2);class写法
class Singleton{
static getInstance(){
if(!Singleton.instance){
Singleton.instance = new Singleton();
}
return Singleton.instance;
}
}
let s1 = Singleton.getInstance();
let s2 = Singleton.getInstance();
console.log(s1 === s2);//true实例1
实现一个 Storage
①Storage--class实现
class Storage {
static getInstance() {
if (!Storage.instance) {
Storage.instance = new Storage();
}
return Storage.instance;
}
setItem(key, value) {
return localStorage.setItem(key, value);
}
getItem(key) {
return localStorage.getItem(key);
}
}
//调用
let s1 = Storage.getInstance();
s1.setItem("a", 666);
let s2 = Storage.getInstance();
console.log(s2.getItem("a"));②闭包实现
// 基础的StorageBase类，把getItem和setItem方法放在它的原型链上
function storageBase() {
storageBase.prototype.getItem = function(key) {
return localStorage.getItem(key);
}
storageBase.prototype.setItem = function(key, value) {
return localStorage.setItem(key, value);
}
}
const Storage = (function() {
let instance = null;
return function() {
if (!instance) {
instance = new storageBase();
}
return instance;
}
})()
let s3 = new Storage();
console.log(s3.getItem('a'));实例2
实现一个全局唯一的Modal弹框
index.html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
#my-modal {
height: 200px;
width: 200px;
line-height: 200px;
position: fixed;
left: 50%;
top: 50%;
transform: translate(-50%, -50%);
border: 1px solid black;
text-align: center;
}
</style>
</head>
<body>
<button id="open" type="button">打开</button>
<button id="close" type="button">关闭</button>
</body>
<script src="./modal.js"></script>
<script>
document.getElementById('open').addEventListener('click', function() {
let modal = Modal.getInstance();
modal.style.display = 'block';
})
document.getElementById('close').addEventListener('click', function() {
let modal = Modal.getInstance();
modal.style.display = 'none';
})
</script>
</html>modal.js
class Modal {
static getInstance() {
if (!Modal.instance) {
let modal = document.createElement('div');
modal.innerHTML = '全局弹窗';
Modal.instance = modal;
modal.id = 'my-modal';
modal.style.display = 'none';
document.body.appendChild(modal);
}
return Modal.instance;
}
}Last updated