Detailed explanation of how JavaScript determines whether to enable cookies and operate cookie codes

Determine whether to enable cookies

<script>
 function checkCookie() {
  var result=false;
  if(navigator.cookiesEnabled){ return true; }
  document.cookie = "testcookie=yes;";
  
  var setCookie = document.cookie;
  
  if (setCookie.indexOf("testcookie=yes") > -1){
   result=true;
  }else{
   document.cookie = "";
  }
  
  return result;
 }
  
  if(!checkCookie()){
  alert("对不起，您的浏览器的Cookie功能被禁用，请开启"); 
  }else{
  alert("Cookie 成功开启");
  }
</script>

Operation cookie

// 1. 设置COOKIE
  
// 简单型
  
function setCookie(c_name,value,expiredays)
{
var exdate=new Date()
exdate.setDate(exdate.getDate()+expiredays)
  
document.cookie=c_name+ "=" +escape(value)+
((expiredays==null) ? "" : ";expires="+exdate.toGMTString())
}
  
// 完整型
function SetCookie(name,value,expires,path,domain,secure)
{
var expDays = expires*24*60*60*1000;
  
var expDate = new Date();
expDate.setTime(expDate.getTime()+expDays);
  
var expString = ((expires==null) ? "" : (";expires=”+expDate.toGMTString()))
var pathString = ((path==null) ? "" : (";path="+path))
var domainString = ((domain==null) ? "" : (";domain="+domain))
var secureString = ((secure==true) ? ";secure" : "" )
document.cookie = name + "=" + escape(value) + expString + pathString + domainString + secureString;
}
  
  
// 2．获取指定名称的cookie值：
  
function getCookie(c_name)
{
if (document.cookie.length>0)
 {
 c_start=document.cookie.indexOf(c_name + "=")
 if (c_start!=-1)
 {
 c_start=c_start + c_name.length+1
 c_end=document.cookie.indexOf(";",c_start)
 if (c_end==-1) c_end=document.cookie.length
 return unescape(document.cookie.substring(c_start,c_end))
 }
 }
return ""
}
  
  
// 3．删除指定名称的cookie：
  
function ClearCookie(name)
{
var expDate = new Date();
expDate.setTime(expDate.getTime()-100);
  
document.cookie=name+”=;expires=”+expDate.toGMTString();
  
}
  
// 4. 检测cookie：
  
function checkCookie()
{
username=getCookie('username')
if (username!=null && username!="")
 {alert('Welcome again '+username+'!')}
else
 {
 username=prompt('Please enter your name:',"")
 if (username!=null && username!="")
 {
 setCookie('username',username,365)
 }
 }
}

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