localstorage本地存储

1. 持久化存储 数据永久保存在那里，不会消失 localStorage 是前端编程中用于持久化存储数据的一种技术实现 2. localStorage是持久化存储对象

      //存储数据
      localStorage.setItem(key,value)
          => key字符串类型
          => value基本数据类型，如果是对象，需要转成字符串
      //获取数据
      let value = localStorage.getItem(key)
   
      //删除数据
      localStorage.removeItem(key)
   
      //清除所有数据
      localStorage.clear()
       
   

   3. 查看localStorage存储数据

` //持久化存储用户信息 localStorage.setItem('username','admin')
localStorage.setItem('age',20)

        let obj = {username:'admin',age:20}
        let str = JSON.stringify(obj)
        localStorage.setItem('user',str )`

``  //获取数据
            let username = localStorage.getItem('username')
            console.log('username = ',username);
            let age = localStorage.getItem('age')
            console.log('age = ',age);

            let user = localStorage.getItem('user')
            user = JSON.parse(user)
            console.log(user.username, user.age);
``

`
            //点击删除按钮删除localStorage中名为username的数据
            const btn = document.querySelector('.del')
            const btnAll = document.querySelector('.delAll')

            btn.addEventListener('click',()=>{
                localStorage.removeItem('username')
            })

            btnAll.onclick = function(){
                localStorage.clear()
            }`