javascript - 如何检查 cookie 是否存在？

Question

检查 cookie 是否存在的好方法是什么？

条件:

如果 Cookie 存在

cookie1=;cookie1=345534;
//or
cookie1=345534;cookie1=;
//or
cookie1=345534;

如果 Cookie 不存在

cookie=;
//or
<blank>

Answer 1

你可以用你想要的 cookie 的名称调用函数 getCookie，然后检查它是否 = null。

function getCookie(name) {
    var dc = document.cookie;
    var prefix = name + "=";
    var begin = dc.indexOf("; " + prefix);
    if (begin == -1) {
        begin = dc.indexOf(prefix);
        if (begin != 0) return null;
    }
    else
    {
        begin += 2;
        var end = document.cookie.indexOf(";", begin);
        if (end == -1) {
        end = dc.length;
        }
    }
    // because unescape has been deprecated, replaced with decodeURI
    //return unescape(dc.substring(begin + prefix.length, end));
    return decodeURI(dc.substring(begin + prefix.length, end));
} 

function doSomething() {
    var myCookie = getCookie("MyCookie");

    if (myCookie == null) {
        // do cookie doesn't exist stuff;
    }
    else {
        // do cookie exists stuff
    }
}