什么是 cookie?

cookie 就是页面用来保存信息,比如自动登录、记住用户名等等。

cookie 的特点

  1. 同个网站中所有的页面共享一套 cookie
  2. cookie 有数量、大小限制
  3. cookie 有过期时间jquery.cookie.js 是一款轻量级的 cookie 插件,可以读取,写入和删除 cookie。本文主要针对

jquery.cookie.js 的用法进行详细的介绍。

jquery.cookie.js 使用方法

Cookies

定义:让网站服务器把少量数据储存到客户端的硬盘或内存,从客户端的硬盘读取数据的一种技术;

下载与引入:jquery.cookie.js基于jquery;先引入jquery,再引入:jquery.cookie.js;

下载:http://plugins.jquery.com/cookie/

<script type="text/javascript" src="js/jquery.min.js"></script>
<script type="text/javascript" src="js/jquery.cookie.js"></script>

使用:

1.添加一个"会话cookie"

$.cookie('the_cookie', 'the_value');

这里没有指明 cookie有效时间,所创建的cookie有效期默认到用户关闭浏览器为止,所以被称为 “会话cookie(session cookie)”。

2.创建一个cookie并设置有效时间为 7天

$.cookie('the_cookie', 'the_value', { expires: 7 });

这里指明了cookie有效时间,所创建的cookie被称为“持久 cookie (persistent cookie)”。注意单位是:天;

3.创建一个cookie并设置 cookie的有效路径

$.cookie('the_cookie', 'the_value', { expires: 7, path: '/' });

在默认情况下,只有设置 cookie的网页才能读取该 cookie。如果想让一个页面读取另一个页面设置的cookie,必须设置cookie的路径。cookie的路径用于设置能够读取 cookie的顶级目录。将这个路径设置为网站的根目录,可以让所有网页都能互相读取 cookie (一般不要这样设置,防止出现冲突)。

4.读取cookie

$.cookie('the_cookie');

5.删除cookie

$.cookie('the_cookie', null);   //通过传递null作为cookie的值即可

6.可选参数

$.cookie('the_cookie','the_value',{
  expires:7, 
  path:'/',
  domain:'jquery.com',
  secure:true
}) 

expires:(Number|Date)有效期;设置一个整数时,单位是天;也可以设置一个日期对象作为Cookie的过期日期;
path:(String)创建该Cookie的页面路径;
domain:(String)创建该Cookie的页面域名;
secure:(Booblean)如果设为true,那么此Cookie的传输会要求一个安全协议,例如:HTTPS;

使用方法:

设置 cookie:

$.cookie('the_cookie', 'the_value');

注:如果 $.cookie 没有第三个参数,那么当浏览器关闭时,该 cookie 将会自动删除。

设置一个有效期为 7 天的 cookie:

$.cookie('the_cookie', 'the_value', {expires: 7});

注:$.cookie 第三个参数是一个对象,除了可以设置有效期(expires: 7),还可以设置有效路径(path: '/')、有效域(domain: 'jquery.com')及安全性(secure: true)。

读取 cookie:

$.cookie('the_cookie');

注:如果没有该 cookie,返回 null。

删除 cookie:

$.cookie('the_cookie', null);

我们只需要给需要删除的 cookie 设置为 null,就可以删除该 cookie。

最后附上源代码:

/**
 * Cookie plugin
 *
 * Copyright (c) 2006 Klaus Hartl (stilbuero.de)
 * Dual licensed under the MIT and GPL licenses:
 * http://www.opensource.org/licenses/mit-license.php
 * http://www.gnu.org/licenses/gpl.html
 *
 */
 
/**
 * Create a cookie with the given name and value and other optional parameters.
 *
 * @example $.cookie('the_cookie', 'the_value');
 * @desc Set the value of a cookie.
 * @example $.cookie('the_cookie', 'the_value', { expires: 7, path: '/', domain: 'jquery.com', secure: true });
 * @desc Create a cookie with all available options.
 * @example $.cookie('the_cookie', 'the_value');
 * @desc Create a session cookie.
 * @example $.cookie('the_cookie', null);
 * @desc Delete a cookie by passing null as value. Keep in mind that you have to use the same path and domain
 * used when the cookie was set.
 *
 * @param String name The name of the cookie.
 * @param String value The value of the cookie.
 * @param Object options An object literal containing key/value pairs to provide optional cookie attributes.
 * @option Number|Date expires Either an integer specifying the expiration date from now on in days or a Date object.
 *    If a negative value is specified (e.g. a date in the past), the cookie will be deleted.
 *    If set to null or omitted, the cookie will be a session cookie and will not be retained
 *    when the the browser exits.
 * @option String path The value of the path atribute of the cookie (default: path of page that created the cookie).
 * @option String domain The value of the domain attribute of the cookie (default: domain of page that created the cookie).
 * @option Boolean secure If true, the secure attribute of the cookie will be set and the cookie transmission will
 *   require a secure protocol (like HTTPS).
 * @type undefined
 *
 * @name $.cookie
 * @cat Plugins/Cookie
 * @author Klaus Hartl/klaus.hartl@stilbuero.de
 */
 
/**
 * Get the value of a cookie with the given name.
 *
 * @example $.cookie('the_cookie');
 * @desc Get the value of a cookie.
 *
 * @param String name The name of the cookie.
 * @return The value of the cookie.
 * @type String
 *
 * @name $.cookie
 * @cat Plugins/Cookie
 * @author Klaus Hartl/klaus.hartl@stilbuero.de
 */
jQuery.cookie = function(name, value, options) {
 if (typeof value != 'undefined') { // name and value given, set cookie
 options = options || {};
 if (value === null) {
  value = '';
  options = $.extend({}, options); // clone object since it's unexpected behavior if the expired property were changed
  options.expires = -1;
 }
 var expires = '';
 if (options.expires && (typeof options.expires == 'number' || options.expires.toUTCString)) {
  var date;
  if (typeof options.expires == 'number') {
  date = new Date();
  date.setTime(date.getTime() + (options.expires * 24 * 60 * 60 * 1000));
  } else {
  date = options.expires;
  }
  expires = '; expires=' + date.toUTCString(); // use expires attribute, max-age is not supported by IE
 }
 // NOTE Needed to parenthesize options.path and options.domain
 // in the following expressions, otherwise they evaluate to undefined
 // in the packed version for some reason...
 var path = options.path ? '; path=' + (options.path) : '';
 var domain = options.domain ? '; domain=' + (options.domain) : '';
 var secure = options.secure ? '; secure' : '';
 document.cookie = [name, '=', encodeURIComponent(value), expires, path, domain, secure].join('');
 } else { // only name given, get cookie
 var cookieValue = null;
 if (document.cookie && document.cookie != '') {
  var cookies = document.cookie.split(';');
  for (var i = 0; i < cookies.length; i++) {
  var cookie = jQuery.trim(cookies[i]);
  // Does this cookie string begin with the name we want?
  if (cookie.substring(0, name.length + 1) == (name + '=')) {
   cookieValue = decodeURIComponent(cookie.substring(name.length + 1));
   break;
  }
  }
 }
 return cookieValue;
 }
};