cookie的用途：用于在客户端存储会话消息
相关API：doument.cookie;
创建cookie:document.cookie = newCookie;
newCookie是一个键值对形成的字符串，由以下几部分组成：
- 名称(name=value)：一个唯一确定的cookie名称
- 域(;domain=domain) :对于哪个域是有效的，如果没有定义，默认为当前文档位置的路径的域名部分
- 有效时间( expires=date-in-GMTString-format) 如果没有定义，cookie会在对话结束时过期 或（ ;max-age=max-age-in-seconds ）
- 路径（;path=path）默认为当前文档位置的路径
- 安全标志(;secure)设置以后，cookie只能通过https协议传输
获取cookie:alert(document.cookie);
cookie的值字符串可以用encodeURIComponent()来保证它不包含任何逗号、分号或空格
以下是一个支持cookie读写的工具库源码
/*
|*|
|*| :: cookies.js ::
|*|
|*| A complete cookies reader/writer framework with full unicode support.
|*|
|*| https://developer.mozilla.org/en-US/docs/DOM/document.cookie
|*|
|*| This framework is released under the GNU Public License, version 3 or later.
|*| http://www.gnu.org/licenses/gpl-3.0-standalone.html
|*|
|*| Syntaxes:
|*|
|*| * docCookies.setItem(name, value[, end[, path[, domain[, secure]]]])
|*| * docCookies.getItem(name)
|*| * docCookies.removeItem(name[, path], domain)
|*| * docCookies.hasItem(name)
|*| * docCookies.keys()
|*|
*/
var docCookies = {
getItem: function (sKey) {
return decodeURIComponent(document.cookie.replace(
new RegExp("(?:(?:^|.*;)\s*" + encodeURIComponent(sKey).replace(/[-.+*]/g, "\$&") + "\s*\=\s*([^;]*).*$)|^.*$"), "$1"))
|| null;
},
setItem: function (sKey, sValue, vEnd, sPath, sDomain, bSecure) {
if (!sKey || /^(?:expires|max-age|path|domain|secure)$/i.test(sKey)) {
return false;
}
var sExpires = "";
if (vEnd) {
switch (vEnd.constructor) {
case Number:
sExpires = vEnd === Infinity ? "; expires=Fri, 31 Dec 9999 23:59:59 GMT" : "; max-age=" + vEnd;
break;
case String:
sExpires = "; expires=" + vEnd;
break;
case Date:
sExpires = "; expires=" + vEnd.toUTCString();
break;
}
}
document.cookie = encodeURIComponent(sKey) +
"=" + encodeURIComponent(sValue) +
sExpires +
(sDomain ? "; domain=" + sDomain : "") +
(sPath ? "; path=" + sPath : "") +
(bSecure ? "; secure" : "");
return true;
},
removeItem: function (sKey, sPath, sDomain) {
if (!sKey || !this.hasItem(sKey)) {
return false;
}
document.cookie = encodeURIComponent(sKey) +
"=; expires=Thu, 01 Jan 1970 00:00:00 GMT" +
( sDomain ? "; domain=" + sDomain : "") +
( sPath ? "; path=" + sPath : "");
return true;
},
hasItem: function (sKey) {
return (new RegExp("(?:^|;\s*)" + encodeURIComponent(sKey).replace(/[-.+*]/g, "\$&") + "\s*\=")).test(document.cookie);
},
/* optional method: you can safely remove it! */
keys: function () {
var aKeys = document.cookie.replace(/((?:^|s*;)[^=]+)(?=;|$)|^s*|s*(?:=[^;]*)?(?:1|$)/g, "").split(/s*(?:=[^;]*)?;s*/);
for (var nIdx = 0; nIdx < aKeys.length; nIdx++) {
aKeys[nIdx] = decodeURIComponent(aKeys[nIdx]);
}
return aKeys;
}
};