<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>改写自菜鸟教程(runoob.com)</title>
</head>
<head>
<script>
function deleteCookie(cname){
document.cookie = cname+"=; expires=Thu, 01 Jan 1970 00:00:00 GMT";
}
function setCookie(cname,cvalue,exdays){
var d = new Date();
d.setTime(d.getTime()+(exdays*24*60*60*1000));
var expires = "expires="+d.toGMTString();
document.cookie = cname+"="+cvalue+"; "+expires;
}
function getCookie(cname){
console.log(document.cookie);
var name = cname + "=";
var ca = document.cookie.split(‘;‘);
for(var i=0; i<ca.length; i++) {
var c = ca[i].trim();
if (c.indexOf(name)==0) { return c.substring(name.length,c.length); }
}
return "";
}
function checkCookie(){
var user=getCookie("username");
if (user!=""){
alert("欢迎 " + user + " 再次访问");
}
else {
user = prompt("请输入你的名字:","");
if (user!="" && user!=null){
setCookie("username",user,30/24/60/60);
}
}
}
</script>
</head>
<body onload="checkCookie()"></body>
<button onclick="deleteCookie(‘username‘)">清楚cookie</button>
</html>
原文：https://www.cnblogs.com/anxiaoyu/p/9083799.html