本地存储WebStorage

WebStorage （js 本地存储)

存储大小一般支持 5MB (不同浏览器可能还不一样)

浏览器通过 Window.sessionStorage 和 Window.localStorage 属性来实现本地存储机制

相关API

• XXXStorage.setItem(‘key’,'value) 该方法接受一个键和值作为参数，会把键值添加到存储中，如果键名存在，则更新其对应的值，
• xxxStorage.getItem(‘key’) 该方法接受一个键名作为参数，返回键名对应的值。
• xxxStorge.removeItem(‘key’) 该方法接受一个键名作为参数，并把该键名从存储中删除
• xxxStorage.clear() 该方法会清空存储中的所有数据。

备注

• SessionStorage 存储的内容会随着浏览器的关闭而消息
• LocalStorage 存储的内容，需要手动清除才会消失

localStorage:

<h2>localStorage</h2>
<button onclick="saveDate()">点我保存数据</button><br/>
<button onclick="readDate()">点我读数据</button><br/>
<button onclick="deleteDate()">点我删除数据</button><br/>
<button onclick="deleteAllDate()">点我清空数据</button><br/>

<script>
  let person = {name:"JOJO",age:20}

  function saveDate(){
    localStorage.setItem('msg','localStorage')
    localStorage.setItem('person',JSON.stringify(person))
  }
  function readDate(){
    console.log(localStorage.getItem('msg'))
    const person = localStorage.getItem('person')
    console.log(JSON.parse(person))
  }
  function deleteDate(){
    localStorage.removeItem('msg')
    localStorage.removeItem('person')
  }
  function deleteAllDate(){
    localStorage.clear()
  }
</script>
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sessionStorage

<h2>sessionStorage</h2>
<button onclick="saveDate()">点我保存数据</button><br/>
<button onclick="readDate()">点我读数据</button><br/>
<button onclick="deleteDate()">点我删除数据</button><br/>
<button onclick="deleteAllDate()">点我清空数据</button><br/>

<script>
  let person = {name:"JOJO",age:20}

  function saveDate(){
    sessionStorage.setItem('msg','sessionStorage')
    sessionStorage.setItem('person',JSON.stringify(person))
  }
  function readDate(){
    console.log(sessionStorage.getItem('msg'))
    const person = sessionStorage.getItem('person')
    console.log(JSON.parse(person))
  }
  function deleteDate(){
    sessionStorage.removeItem('msg')
    sessionStorage.removeItem('person')
  }
  function deleteAllDate(){
    sessionStorage.clear()
  }
</script>

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使用本地存储优化Todo-list

<template>
	<div id="root">
		<div class="todo-container">
			<div class="todo-wrap">
				<MyHeader :addTodo="addTodo"/>
				<MyList :todos="todos" :checkTodo="checkTodo" :deleteTodo="deleteTodo"/>
				<MyFooter :todos="todos" :checkAllTodo="checkAllTodo" :clearAllTodo="clearAllTodo"/>
			</div>
		</div>
	</div>
</template>

<script>
	import MyHeader from './components/MyHeader'
	import MyList from './components/MyList'
	import MyFooter from './components/MyFooter.vue'

	export default {
		name:'App',
		components:{MyHeader,MyList,MyFooter},
		data() {
			return {
				// 🔴从本地存储中获得数据，null就创建空数组[]
				todos:JSON.parse(localStorage.getItem('todos')) || []
			}
		},
		methods: {
			//添加一个todo
			addTodo(todoObj){
				this.todos.unshift(todoObj)
			},
			//勾选or取消勾选一个todo
			checkTodo(id){
				this.todos.forEach((todo)=>{
					if(todo.id === id) todo.done = !todo.done
				})
			},
			//删除一个todo
			deleteTodo(id){
				this.todos = this.todos.filter( todo => todo.id !== id )
			},
			//全选or取消全选
			checkAllTodo(done){
				this.todos.forEach((todo)=>{
					todo.done = done
				})
			},
			//清除所有已经完成的todo
			clearAllTodo(){
				this.todos = this.todos.filter((todo)=>{
					return !todo.done
				})
			}
		},
    // 🔴数据发生改变就放到本地存储中，注意深度侦听，以及JSON转化为字符串
		watch: {
			todos:{
				deep:true,
				handler(value){
					localStorage.setItem('todos',JSON.stringify(value))
				}
			}
		},
	}
</script>
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