一个javascript的Cookie读写删的通用代码

function writeCookie(name, value, days) {
var expires = "";
if (days) {
var date = new Date();
date.setTime(date.getTime() + (days * 24 * 60 * 60 * 1000));
expires = "; expires=" + date.toGMTString();
}

document.cookie = name + "=" + value + expires + "; path=/";
}

function readCookie(name) {
var searchName = name + "=";
var cookies = document.cookie.split(";");
for(var i=0; i < cookies.length; i++) {
var c = cookies[i];
while (c.charAt(0) == ' ')
c = c.substring(1,c.length);
if (c.indexOf(searchName) == 0)
return c.substring(searchName.length,c.length);
}
return null;
}

function eraseCookie(name) {
writeCookie(name,"",-1);
}