代码如下：

<script>
// 读取Cookie
function GetCookie(cookieName) {
var arg = cookieName + "=";
var alen = arg.length;
var clen = document.cookie.length;
var i = 0;
while (i < clen){
var j = i + alen;
if(document.cookie.substring(i, j) == arg )
return getCookieVal(j);
i = document.cookie.indexOf("", i) + 1;
if(i == 0)
break;
}
return null;
}
function getCookieVal(cookieOffset) {
var endstr = document.cookie.indexOf(";", cookieOffset);
if(endstr == -1)
endstr = document.cookie.length;
return unescape(document.cookie.substring(cookieOffset,endstr));
}
// 写入Cookie
function SetCookie (cookieName, cookieValue) {
var argv = arguments;
var argc = arguments.length;
var expires = (argc>2) ? argv[2] : null;
var path = (argc>3) ? argv[3] : null;
var domain = (argc>4) ? argv[4] : null;
var secure = (argc>5) ? argv[5] : false;
document.cookie = cookieName + "=" + escape(cookieValue) +
((expires==null)?"":(";expires=" + expires.toGMTString())) +
((path==null)?"":(";path="+path)) +
((domain==null)?"":(";domain="+ domain)) +
((secure==true)?";secure":"");
}
<script>