javascript cookie

Posted slgkaifa

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篇首语:本文由小常识网(cha138.com)小编为大家整理,主要介绍了javascript cookie相关的知识,希望对你有一定的参考价值。

一、什么是 cookie?

cookie 就是页面用来保存信息,比方自己主动登录、记住username等等。

二、cookie 的特点

  1. 同个站点中全部的页面共享一套 cookie
  2. cookie 有数量、限制大小
  3. cookie 有过期时间

三、怎样使用 cookie?

通过 document.cookie 来写入 cookie

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<!DOCTYPE html>
<html lang="en-US">
<head>
    <meta charset="UTF-8">
    <title>cookie基础</title>
</head>
<body>
    
</body>
</html>
<script type="text/javascript">
document.cookie = \'username=abc\';
document.cookie = \'password=123\';
document.cookie = \'email=abcdef@123.com\';
</script>
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打开浏览器查看 cookie,能够发现新定义的 cookie 并不会将原来的覆盖。

假设没有设置过期时间,那么关闭浏览器就会清空 cookie。

怎样设置过期时间呢?答案是:expires。一般我们会结合 Date 对象来使用。

var d = new Date();
d.setTime(d.getTime() + 1 * 3600 * 1000);
document.cookie = \'username=abc; expires=\' + d.toGMTString();

我们能够通过火狐浏览器看到,username 的过期时间是当前时间的 1 小时后。

最后对获取 cookie 的方法进行封装:

function setCookie(name,value,hours){  
    var d = new Date();
    d.setTime(d.getTime() + hours * 3600 * 1000);
    document.cookie = name + \'=\' + value + \'; expires=\' + d.toGMTString();
}

学会了怎样设置 cookie,那么该怎样读取 cookie 呢?

首先我们看下 cookie 里的内容是什么类型?

document.cookie = \'username=abc\';
document.cookie = \'password=123\';
document.cookie = \'email=abcdef@123.com\';
typeof document.cookie;    //string
alert(document.cookie);    //\'username=abc; password=123; email=abcdef@123.com\'

得到的是一串字符串。须要注意的是。每一个 ; 后面都有个空格。

那么我们怎样取到详细的数值呢?附上代码:

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function getCookie(name){  
    var arr = document.cookie.split(\'; \');
    for(var i = 0; i < arr.length; i++){
        var temp = arr[i].split(\'=\');
        if(temp[0] == name){
            return temp[1];
        }
    }
    return \'\';
}
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除了设置、获取 cookie,我们还能够删除 cookie。我们在网上常常看到有清除username这种功能。事实上就是用到了清除 cookie。

清除 cookie 事实上非常easy,仅仅要使过期时间为过去时间就能够了。

function removeCookie(name){
    var d = new Date();
    d.setTime(d.getTime() - 10000);
    document.cookie = name + \'=1; expires=\' + d.toGMTString();
}

最后我们将设置、获取、清除 cookie 封装成一个 cookie.js

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function setCookie(name,value,hours){  
    var d = new Date();
    d.setTime(d.getTime() + hours * 3600 * 1000);
    document.cookie = name + \'=\' + value + \'; expires=\' + d.toGMTString();
}
function getCookie(name){  
    var arr = document.cookie.split(\'; \');
    for(var i = 0; i < arr.length; i++){
        var temp = arr[i].split(\'=\');
        if(temp[0] == name){
            return temp[1];
        }
    }
    return \'\';
}
function removeCookie(name){
    var d = new Date();
    d.setTime(d.getTime() - 10000);
    document.cookie = name + \'=1; expires=\' + d.toGMTString();
}
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jquery.cookie.js 是一款轻量级的 cookie 插件,能够读取,写入和删除 cookie。

本文主要针对 jquery.cookie.js 的使用方法进行具体的介绍。

用法:

设置 cookie:

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

注:假设 $.cookie 没有第三个參数。那么当浏览器关闭时,该 cookie 将会自己主动删除。

设置一个有效期为 7 天的 cookie:

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

注:$.cookie 第三个參数是一个对象,除了能够设置有效期(expires: 7)。还能够设置有效路径(path: \'/\')、有效域(domain: \'jquery.com\')及安全性(secure: true)。

读取 cookie:

$.cookie(\'the_cookie\');

注:假设没有该 cookie,返回 null。

删除 cookie:

$.cookie(\'the_cookie\', null);

我们仅仅须要给须要删除的 cookie 设置为 null。就能够删除该 cookie。

最后附上源码:

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/**
 * 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; } };

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cookie 的应用——记住username

以下我们通过一个实例来应用cookie.js

最常见的就是记住username,当用户登录过一次后,通过 cookie 记录下该用户的账号和password,这样下次打开页面的时候不用再次输入账号password了。附上代码:

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<!DOCTYPE HTML>
<html lang="en-US">
<head>
    <meta charset="UTF-8">
    <title>cookie的应用——记住用户名</title>
</head>
<body>
    <form action="#" id="myform">
        <label for="username">用户名:</label><input type="text" name="username" id="username" />
        <label for="userpass">密码:</label><input type="password" name="userpass" id="userpass" />
        <input type="submit" value="登录" />
        <a href="javascript:;">清除记录</a>
    </form>
</body>
</html>
<script type="text/javascript" src="cookie.js"></script>
<script type="text/javascript">
window.onload = function(){
    var oForm = document.getElementById(\'myform\');
    var oTxt1 = document.getElementById(\'username\');
    var oTxt2 = document.getElementById(\'userpass\');
    var oClear = document.getElementsByTagName(\'a\')[0];
    oTxt1.value = getCookie(\'username\');
    oTxt2.value = getCookie(\'userpass\');
    
    oForm.onsubmit = function(){
        setCookie(\'username\',oTxt1.value,30);
        setCookie(\'userpass\',oTxt2.value,30);
    }
    oClear.onclick = function(){
        removeCookie(\'username\');
        removeCookie(\'userpass\');
        oTxt1.value = \'\';
        oTxt2.value = \'\';
    }
}
</script>
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