HTTP协议

http协议：超文本传输协议 - Hyper Text Transfer Protocol
针对的双方是 客户端 - 服务器，传送的内容是超文本

• 1.建立连接
  客户端跟服务器之间通信之前需要双方确认是否可以进行通信
• 2.开始通信
  客户端给服务器发送请求报文
  服务器对客户端做出相应
• 3.断开连接

cookie

• 设置cookie

function setCookie(key,value,seconds,path='/'){
    var date = new Date()
    date.setTime(date.getTime()+seconds*1000-8*3600*1000)
    document.cookie = `${key}=${value};expires=${date};path=${path}`
}

• 获取cookie

function getCookie(key){
    var cookies = document.cookie;
    var arr = cookies.split(";")
    for(var i=0;i<arr.length;i++){
        var brr = arr[i].split("=")
        if(brr[0]===key){
            return brr[1]
        }
    }
}

• 删除cookie

function removeCookie(key,path='/'){
    setCookie(key,null,-20,path)
}

• demo

var username = getCookie('username')
if(username){
    document.querySelector('.box').innerHTML = '欢迎<span>'+username+'</span>登入<br><a href="javascript:;" class="logout">退出</a>'
    document.querySelector('.logout').onclick = function(){
        if(confirm('你确定要退出吗')){
            removeCookie('username')
            document.querySelector('.box').innerHTML = `
                <a href="login.html">登陆</a>
                <a href="register.html">注册</a>
            `;
        }
    }
}

function setCookie(key,value,seconds,path='/'){
    var date = new Date()
    date.setTime(date.getTime()+seconds*1000-8*3600*1000)
    document.cookie = `${key}=${value};expires=${date};path=${path}`
}

function removeCookie(key,path='/'){
    setCookie(key,null,-20,path)
}

function getCookie(key){
    var cookies = document.cookie;
    var arr = cookies.split(";")
    for(var i=0;i<arr.length;i++){
        var brr = arr[i].split("=")
        if(brr[0]===key){
            return brr[1]
        }
    }
}