装饰器模式
装饰器模式是指在不改变原有对象的基础上, 对其进行包装扩展, 使其满足用户更复杂的需求.
复习下单例模式
使用单例模式维护一个全局的 Modal
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| <!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<meta http-equiv="X-UA-Compatible" content="ie=edge" />
<style>
div {
width: 200px;
height: 200px;
border: 1px solid pink;
color: pink;
position: fixed;
left: 50%;
top: 50%;
transform: translate(-50%, -50%);
}
</style>
<title>Document</title>
</head>
<body>
<button id="open">open</button>
<button id="hidden">hidden</button>
<script>
const Modal = (function() {
let modal = null
return function() {
if (!modal) {
modal = document.createElement('div')
modal.style.display = 'none'
modal.innerText = 'Modal'
document.body.appendChild(modal)
}
return modal
}
})()
document.getElementById('open').addEventListener(
'click',
function() {
const modal = new Modal()
console.log(modal)
modal.style.display = 'block'
},
false
)
document.getElementById('hidden').addEventListener(
'click',
function() {
const modal = new Modal()
modal.style.display = 'none'
},
false
)
</script>
</body>
</html>
|
问题来了
这时候产品经理说, 需要修改下这个按钮文字内容, 还要给点击按钮置灰, 不可点击, 如果我们在项目多处用到的话, 就需要一处处进行修改
如果封装成公共组件, 也会因为组件应用时的需求复杂度而产生同样的问题
装饰器模式改造案例
第一步 抽离原有旧逻辑
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|
const Modal = (function() {
let modal = null
return function() {
if (!modal) {
modal = document.createElement('div')
modal.style.display = 'none'
modal.innerText = 'Modal'
document.body.appendChild(modal)
}
return modal
}
})()
function openModal() {
const modal = new Modal()
if (modal) {
modal.style.display = 'block'
}
}
|
第二步 封装新需求逻辑
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| function changeBtnText() {
const btn = document.getElementById('open')
btn.innerText = '快点我'
}
function disabledBtn() {
const btn = document.getElementById('open')
btn.setAttribute('disabled', true)
}
function changeBtnStatus() {
changeBtnText()
disabledBtn()
}
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第三步 添加需求到点击按钮上
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| document.getElementById('open').addEventListener(
'click',
function() {
openModal()
changeBtnStatus()
},
false
)
|
ES6 class 类实现装饰器
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|
class Modal {
constructor() {
this.modal = null
}
static getModal() {
if (!this.modal) {
this.modal = document.createElement('div')
this.modal.innerText = '我是一个class单例模式下的div'
this.modal.style.display = 'none'
document.body.appendChild(this.modal)
}
return this.modal
}
}
class openModal {
click() {
const modal = Modal.getModal()
modal.style.display = 'block'
}
}
class Decorator {
constructor(open_button) {
this.open_btn = open_button
}
onclick() {
this.open_btn.click()
this.changeBtnStatus()
}
changeBtnStatus() {
this.changeBtnText()
this.disabledBtn()
}
changeBtnText() {
const btn = document.getElementById('open')
btn.innerText = '来点击我啊'
}
disabledBtn() {
const btn = document.getElementById('open')
btn.setAttor = '来点击我啊'
}
}
document.getElementById('open').addEventListener(
'click',
function() {
const openBtn = new openModal()
const btn = new Decorator(openBtn)
btn.onclick()
},
false
)
|
