我找到了两个函数来使用 Javascript 获取 cookie 数据，一个在 w3schools.com 上和一个 quirksmode.org
我想知道我应该使用哪一个？

例如，我相信我在某处读到某些浏览器在拆分 ; 分号时存在问题？

w3schools:

function getCookie(c_name) {
    if (document.cookie.length > 0) {
        c_start = document.cookie.indexOf(c_name + "=");
        if (c_start != -1) {
            c_start = c_start + c_name.length + 1;
            c_end = document.cookie.indexOf(";", c_start);
            if (c_end == -1) c_end = document.cookie.length;
            return unescape(document.cookie.substring(c_start, c_end));
        }
    }
    return "";
}

怪癖模式:

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

最佳答案

W3CSchool 的功能是错误的。如果有多个具有相同后缀的 cookie，它将失败，例如:

ffoo=bar; foo=baz

当您搜索 foo 时，它将返回 ffoo 而不是 foo 的值。

现在我要做的是:首先，您需要了解 cookie 传输的语法。 Netscape 的原始规范(只有副本可用，如 this one at haxx.se )使用分号分隔多个 cookie，而每个名称/值对具有以下语法:

NAME=VALUE
This string is a sequence of characters excluding semi-colon, comma and white space. If there is a need to place such data in the name or value, some encoding method such as URL style %XX encoding is recommended, though no encoding is defined or required.

所以在分号或逗号处拆分 document.cookie 字符串是一个可行的选择。

除此之外，RFC 2109还指定 cookie 由分号或逗号分隔:

cookie          =       "Cookie:" cookie-version
                        1*((";" | ",") cookie-value)
cookie-value    =       NAME "=" VALUE [";" path] [";" domain]
cookie-version  =       "$Version" "=" value
NAME            =       attr
VALUE           =       value
path            =       "$Path" "=" value
domain          =       "$Domain" "=" value

虽然两者都是允许的，但逗号是首选，因为它们是 HTTP 中列表项的默认分隔符。

Note: For backward compatibility, the separator in the Cookie header is semi-colon (;) everywhere. A server should also accept comma (,) as the separator between cookie-values for future compatibility.

此外，名称/值对还有一些进一步的限制，因为 VALUE 也可以是 RFC 2616 中指定的带引号的字符串:

attr        =     token
value       =     token | quoted-string

所以这两个cookie版本需要分开处理:

if (typeof String.prototype.trimLeft !== "function") {
    String.prototype.trimLeft = function() {
        return this.replace(/^\s+/, "");
    };
}
if (typeof String.prototype.trimRight !== "function") {
    String.prototype.trimRight = function() {
        return this.replace(/\s+$/, "");
    };
}
if (typeof Array.prototype.map !== "function") {
    Array.prototype.map = function(callback, thisArg) {
        for (var i=0, n=this.length, a=[]; i<n; i++) {
            if (i in this) a[i] = callback.call(thisArg, this[i]);
        }
        return a;
    };
}
function getCookies() {
    var c = document.cookie, v = 0, cookies = {};
    if (document.cookie.match(/^\s*\$Version=(?:"1"|1);\s*(.*)/)) {
        c = RegExp.$1;
        v = 1;
    }
    if (v === 0) {
        c.split(/[,;]/).map(function(cookie) {
            var parts = cookie.split(/=/, 2),
                name = decodeURIComponent(parts[0].trimLeft()),
                value = parts.length > 1 ? decodeURIComponent(parts[1].trimRight()) : null;
            cookies[name] = value;
        });
    } else {
        c.match(/(?:^|\s+)([!#$%&'*+\-.0-9A-Z^`a-z|~]+)=([!#$%&'*+\-.0-9A-Z^`a-z|~]*|"(?:[\x20-\x7E\x80\xFF]|\\[\x00-\x7F])*")(?=\s*[,;]|$)/g).map(function($0, $1) {
            var name = $0,
                value = $1.charAt(0) === '"'
                          ? $1.substr(1, -1).replace(/\\(.)/g, "$1")
                          : $1;
            cookies[name] = value;
        });
    }
    return cookies;
}
function getCookie(name) {
    return getCookies()[name];
}

关于Javascript getCookie 函数，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/4003823/