JavaScript 检查cookie

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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){
  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("Welcome again " + user);
  }
  else{
    user=prompt("Please enter your name:","")
    if(user!=""&&user!=null){
      setCookie("username", user,30);
    }
  }
}
JavaScript