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 "";
}

document.cookie = "user=xiaoming";

var user=getCookie("user");

alert(user);