在JavaScript中按名称读取cookie的最短函数是什么？

问题描述

在JavaScript中阅读Cookie的最短，准确和跨浏览器兼容的方法是什么？

独立的脚本（其中我不能有任何外部依赖），我发现我添加了一个函数读取cookie，通常落在方法（280个字节，216个缩写）

Very often, while building stand-alone scripts (where I can't have any outside dependencies), I find myself adding a function for reading cookies, and usually fall-back on the QuirksMode.org readCookie() method (280 bytes, 216 minified.)

function readCookie(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;
}

它的工作，但它的丑陋，并增加了一点膨胀每一次。

It does the job, but its ugly, and adds quite a bit of bloat each time.

使用类似这样的东西（修改，165字节，125缩小）：

The method that jQuery.cookie uses something like this (modified, 165 bytes, 125 minified):

function read_cookie(key)
{
    var result;
    return (result = new RegExp('(?:^|; )' + encodeURIComponent(key) + '=([^;]*)').exec(document.cookie)) ? (result[1]) : null;
}

注意竞争：我有理由减少我的readCookie函数的大小，并确保我的解决方案是有效的。

Note this is not a 'Code Golf' competition: I'm legitimately interested in reducing the size of my readCookie function, and in ensuring the solution I have is valid.

推荐答案

这只会遇到document.cookie一次。每个后续请求都将是即时的。

This will only ever hit document.cookie ONE time. Every subsequent request will be instant.

(function(){
    var cookies;

    function readCookie(name,c,C,i){
        if(cookies){ return cookies[name]; }

        c = document.cookie.split('; ');
        cookies = {};

        for(i=c.length-1; i>=0; i--){
           C = c[i].split('=');
           cookies[C[0]] = C[1];
        }

        return cookies[name];
    }

    window.readCookie = readCookie; // or expose it however you want
})();

恐怕真的没有比这个一般逻辑更快的方法，除非你自由使用 .forEach 这是与浏览器有关的（即使那样你不会节省太多）

I'm afraid there really isn't a faster way than this general logic unless you're free to use .forEach which is browser dependent (even then you're not saving that much)

稍微压缩到 120字节：

function read_cookie(k,r){return(r=RegExp('(^|; )'+encodeURIComponent(k)+'=([^;]*)').exec(document.cookie))?r[2]:null;}

如果你做的话，你可以得到 110 bytes 如果你删除 encodeURIComponent ，它是一个1个字母的函数名， 90个字节。

You can get it to 110 bytes if you make it a 1-letter function name, 90 bytes if you drop the encodeURIComponent.

我已经得到 73字节，但公平的是 82字节当添加 encodeURIComponent 时命名为 readCookie 和 102个字节

I've gotten it down to 73 bytes, but to be fair it's 82 bytes when named readCookie and 102 bytes when then adding encodeURIComponent:

function C(k){return(document.cookie.match('(^|; )'+k+'=([^;]*)')||0)[2]}

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