写入document.cookie需要多长时间

Question

想知道写入 document.cookie 需要多长时间。在设置 cookie 并重新定向到另一个页面并且 document.cookie 未设置时遇到边缘情况。似乎在桌面（Chrome、firefox）与 iphone/平板电脑（safari）上有不同的性能

当我添加大约 500 毫秒的设置超时时，似乎在所有情况下都能正常工作

// 写出 cookie

   function set_cookie(name, value ) {
        var date =  new Date();
        date.setTime(date.getTime() + (365 * 24 * 60 * 60 * 1000)); 
        var cookie = name + "=" + value + "; expires=" + date.toGMTString() + ";";
        document.cookie = cookie;

    }

//读取cookie

function read_Cookie(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) {
                var cVal = c.substring(nameEQ.length, c.length);
                return cVal;
            }
        }
        return null;
    }

//按钮点击设置cookie和导航

        $("#goToWebButton").click(function() {
             if ($('#chkDontShow').attr('checked') == 'checked') {
                set_cookie('IgnoreInAppLink','web');
               }
            setTimeout(function(){window.location.href = '';}, 500);
        });

        $("#goToAppButton").click(function() {
          if ($('#chkDontShow').attr('checked') == 'checked') {
                set_cookie('IgnoreInAppLink','app');
            }
            setTimeout(function(){window.location.href = '';},500);

        });

Answer 1

JavaScript 本质上是单线程的，因此无论花费多长时间（几乎是瞬时的），在写入 cookie 之前都不应执行重定向。也就是说，正如Is JavaScript guaranteed to be single-threaded? 指出的那样，情况可能并非总是如此。为了缓解这种情况，您可以考虑使用 jQuery 的延迟对象：

function set_cookie(name,value,deferred) { // added deferred argument
    var date =  new Date();
    date.setTime(date.getTime() + (365 * 24 * 60 * 60 * 1000)); 
    var cookie = name + "=" + value + "; expires=" + date.toGMTString() + ";";
    document.cookie = cookie;
    deferred.resolve();
}

var deferred = $.Deferred();

deferred.done(function() {
    window.location.href = "";
});

$("#goToAppButton").click(function() {
    if ($("#chkDontShow").attr("checked") == "checked") {
        set_cookie("IgnoreInAppLink","web",deferred);
    } else {
        deferred.resolve();
    }
}