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23. 本地存储 ​

WebStorage (js 本地存储) ​

存储内容大小一般支持5MB左右(不同浏览器可能还不一样)

浏览器端通过 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，会把键值对添加到存储中，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
  • xxxStorage.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窗口关闭而消失
  • LocalStorage存储的内容，需要手动清除才会消失
  • xxxStorage.getItem(xxx)如果xxx对应的value获取不到，那么getItem()的返回值是null
  • JSON.parse(null)的结果依然是null

localStorage ​

html
<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>localStorage</title>
</head>

<body>
  <h2>localStorage</h2>
  <button onclick="saveData()">点我保存一个数据</button>
  <button onclick="readData()">点我读取一个数据</button>
  <button onclick="deleteData()">点我删除一个数据</button>
  <button onclick="clearData()">点我清空一个数据</button>

  <script>
    let p = { name: '张三', age: 18 }
    function saveData() {
      localStorage.setItem('msg', JSON.stringify(p))
    }

    function readData() {
      console.log(localStorage.getItem('msg'));
    }

    function deleteData() {
      localStorage.removeItem('msg')
    }

    function clearData() {
      localStorage.clear()
    }

  </script>
</body>

</html>

sessionStorage ​

html
<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>sessionStorage</title>
</head>

<body>
  <h2>sessionStorage</h2>
  <button onclick="saveData()">点我保存一个数据</button>
  <button onclick="readData()">点我读取一个数据</button>
  <button onclick="deleteData()">点我删除一个数据</button>
  <button onclick="clearData()">点我清空一个数据</button>

  <script>
    let p = { name: '张三', age: 18 }
    function saveData() {
      sessionStorage.setItem('msg', JSON.stringify(p))
    }

    function readData() {
      console.log(sessionStorage.getItem('msg'));
    }

    function deleteData() {
      sessionStorage.removeItem('msg')
    }

    function clearData() {
      sessionStorage.clear()
    }

  </script>
</body>

</html>

使用本地存储优化 Todo-List ​

App.vue ​

vue
<template>
  <div>
    <div id="root">
      <div class="todo-container">
        <div class="todo-wrap">
          <MyHeader :addTodo="addTodo"></MyHeader>
          <MyList :deleteTodo="deleteTodo" :checkTodo="checkTodo" :todos="todos"></MyList>
          <MyFooter :clearAllTodo="clearAllTodo" v-if="todos.length > 0" :fullCheck="fullCheck" :todos="todos"></MyFooter>
        </div>
      </div>
    </div>
  </div>
</template>

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

export default {
  name: 'App',
  watch: {
    todos: {
      deep: true,
      handler(value) {
        localStorage.setItem('todos', JSON.stringify(value))
      }
    }
  },
  data() {
    return {
      // 由于 todos 是 MyHeader组件和MyFooter组件都在使用 所以放在 App 中 （状态提升）
      todos: JSON.parse(localStorage.getItem('todos')) || []
    }
  },
  components: {
    MyHeader,
    MyFooter,
    MyList
  },
  mounted() {},

  methods: {
    // 添加一个 todo
    addTodo(todoObj) {
      this.todos.unshift(todoObj)
    },
    // 勾选 or 取消勾选 todo
    checkTodo(id) {
      this.todos.some(todo => {
        if (todo.id == id) {
          todo.done = !todo.done
          console.log(todo)
        }
      })
    },
    // 删除一个todo
    deleteTodo(id) {
      this.todos = this.todos.filter(todo => {
        return todo.id !== id
      })
    },
    // 全选 or 取消全选
    fullCheck(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 => !todo.done)
    }
  }
}
</script>

<style lang="less">
/*base*/
body {
  background: #fff;
}

.btn {
  display: inline-block;
  padding: 4px 12px;
  margin-bottom: 0;
  font-size: 14px;
  line-height: 20px;
  text-align: center;
  vertical-align: middle;
  cursor: pointer;
  box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.2), 0 1px 2px rgba(0, 0, 0, 0.05);
  border-radius: 4px;
}

.btn-danger {
  color: #fff;
  background-color: #da4f49;
  border: 1px solid #bd362f;
}

.btn-danger:hover {
  color: #fff;
  background-color: #bd362f;
}

.btn:focus {
  outline: none;
}

.todo-container {
  width: 600px;
  margin: 0 auto;
}
.todo-container .todo-wrap {
  padding: 10px;
  border: 1px solid #ddd;
  border-radius: 5px;
}
</style>

MyList.vue ​

vue
<template>
  <div>
    <ul class="todo-main">
      <MyItem
      v-for="todoObj in todos"
      :key="todoObj.id"
      :todo="todoObj"
      :checkTodo="checkTodo"
      :deleteTodo="deleteTodo"
      >
      </MyItem>
    </ul>
  </div>
</template>

<script>
import MyItem from './MyItem.vue'
export default {
  name: 'MyList',

  data() {
    return {}
  },
  props: ['todos', 'checkTodo','deleteTodo'],
  components: {
    MyItem
  },

  mounted() {},

  methods: {}
}
</script>

<style lang="less" scoped>
/*main*/
.todo-main {
  margin-left: 0px;
  border: 1px solid #ddd;
  border-radius: 2px;
  padding: 0px;
}

.todo-empty {
  height: 40px;
  line-height: 40px;
  border: 1px solid #ddd;
  border-radius: 2px;
  padding-left: 5px;
  margin-top: 10px;
}
</style>

MyItem.vue ​

vue
<template>
  <div>
    <li>
      <label>
        <input type="checkbox" :checked="todo.done" @change="handle(todo.id)" />
        <!-- 如下代码也能实现功能，但是不太推荐，因为有点违反原则，因为修改了props -->
        <!-- <input type="checkbox" v-model="todo.done"> -->
        <span>{{ todo.title }}</span>
      </label>
      <button class="btn btn-danger" @click="deleteItem(todo.id)">删除</button>
    </li>
  </div>
</template>

<script>
export default {
  name: 'MyItem',

  data() {
    return {}
  },

  // 声明接收 todo 对象
  props: ['todo', 'checkTodo','deleteTodo'],

  mounted() {},

  methods: {
    handle(id) {
      // 通知 App  组件将对应的数据 取反
      this.checkTodo(id)
    },
    deleteItem(id) {
      if (confirm('确定删除吗')) {
        // 通知 App 删除指定 id
        this.deleteTodo(id)
      }
    }
  }
}
</script>

<style lang="less" scoped>
/*item*/
li {
  list-style: none;
  height: 36px;
  line-height: 36px;
  padding: 0 5px;
  border-bottom: 1px solid #ddd;
}

li label {
  float: left;
  cursor: pointer;
}

li label li input {
  vertical-align: middle;
  margin-right: 6px;
  position: relative;
  top: -1px;
}

li button {
  float: right;
  display: none;
  margin-top: 3px;
}

li:before {
  content: initial;
}

li:last-child {
  border-bottom: none;
}
li:hover {
  background-color: gainsboro;
}

li:hover button {
  display: block;
}
</style>

MyHeader.vue ​

vue
<template>
  <div>
    <div class="todo-header">
      <input type="text" placeholder="请输入你的任务名称，按回车键确认" v-model="title" @keyup.enter="add" />
    </div>
  </div>
</template>

<script>
import { nanoid } from 'nanoid'
export default {
  name: 'MyHeader',

  data() {
    return {
      title: ''
    }
  },

  props: ['addTodo'],
  mounted() {},

  methods: {
    add() {
      // 校验数据
      if (!this.title.trim()) return alert('输入不能为空')
      // 将用户的输入包装成一个todo对象
      const todoObj = { id: nanoid(), title: this.title.trim(), done: false }
      // 通知App组件去添加一个 todo 对象
      this.addTodo(todoObj)
      // 清空输入
      this.title = ''
    }
  }
}
</script>

<style lang="less" scoped>
/*header*/
.todo-header input {
  width: 560px;
  height: 28px;
  font-size: 14px;
  border: 1px solid #ccc;
  border-radius: 4px;
  padding: 4px 7px;
}

.todo-header input:focus {
  outline: none;
  border-color: rgba(82, 168, 236, 0.8);
  box-shadow: inset 0 1px 1px rgba(0, 0, 0, 0.075), 0 0 8px rgba(82, 168, 236, 0.6);
}
</style>

MyFooter.vue ​

vue
<template>
  <div>
    <div class="todo-footer">
      <label>
        <input type="checkbox" v-model="isAll" />
      </label>
      <span>
        <span>已完成{{ doneTotal }}</span> / 全部{{ todos.length }}
      </span>
      <button class="btn btn-danger" @click="clearTodos">清除已完成任务</button>
    </div>
  </div>
</template>

<script>
export default {
  name: 'MyFooter',
  computed: {
    doneTotal() {
      return this.todos.filter(todo => todo.done).length
    },
    isAll: {
      get() {
        return this.todos.every(todo => todo.done == true) && this.todos.length > 0
      },
      set(value) {
        this.fullCheck(value)
      }
    }
  },
  data() {
    return {
      isfull: false
    }
  },
  props: ['fullCheck', 'todos', 'clearAllTodo'],

  mounted() {},
  methods: {
    clearTodos() {
      if (confirm('确定清空吗')) {
        this.clearAllTodo()
      }
    }
  }
}
</script>

<style lang="less" scoped>
/*footer*/
.todo-footer {
  height: 40px;
  line-height: 40px;
  padding-left: 6px;
  margin-top: 5px;
}

.todo-footer label {
  display: inline-block;
  margin-right: 20px;
  cursor: pointer;
}

.todo-footer label input {
  position: relative;
  top: -1px;
  vertical-align: middle;
  margin-right: 5px;
}

.todo-footer button {
  float: right;
  margin-top: 5px;
}
</style>

main.js ​

js
//引入Vue
import Vue from 'vue'
//引入App
import App from './App.vue'
//关闭Vue的生产提示
Vue.config.productionTip = false

//创建vm
new Vue({
	el:'#app',
	render: h => h(App)
})

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