localstorage(常用)

sessionstorage

<script>
    const login_btn = document.querySelector("#btn")
    const user_name = document.querySelector("#user_name")
    const user_password = document.querySelector("#user_password")
    const usermegs = document.querySelector("#usermegs")
    login_btn.onclick = function () {
        const usermeg = JSON.stringify({
            user_name: user_name.value,
            user_password: user_password.value
        })

        if (user_name.value != '' && user_password.value != '') {
            login_btn.style.cssText = "visibility: hidden;"
            window.localStorage.setItem("usermeg", usermeg)
           let  getusermeg = JSON.parse(window.localStorage.getItem("usermeg"))
           usermegs.innerHTML =`用户名为:${getusermeg.user_name}密码为:${getusermeg.user_password}`
           
        }
        user_name.value = ''
        user_password.value = ''
    }
</script>

localStorage不主动删除,永远不会销毁

cookie

存在跨域问题 联系的时候不要再浏览器中打开会产生跨域要在本地服务器打开
错误

正确

1.基本语法
添加


设置过期时间

删除

封装

<script>
    //增加
    function setcookie(name, value, day) {
        let cdate = new Date()
        cdate.setDate(cdate.getDate() + day)
        document.cookie = `${name}=${value};expires=` + cdate
    }
    //查找
    function getcookie(name) {
        let str = document.cookie
        //遍历每一组
        let arr = str.split("; ")
        for (a of arr) {
            //取到key
            let cookievalue = a.split("=")
            if (cookievalue[0] == name) {
                return cookievalue[1]
            }
        }
    }
    //删除
    function removecookie(name) {
        setcookie(name, {}, -1)
    }
</script>