cookie的使用

<pre name="code" class="javascript">嘎嘎嘎   

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 ""
	}

function setCookie(c_name, value, expiredays) {
	var exdate = new Date();
	exdate.setDate(exdate.getDate()+expiredays);
	document.cookie = c_name + "=" + escape(value) + ";expires=" + exdate.toGMTString();
}

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);
		}
	}
}