javascript - JavaScript 中的 Facebook 服务器时间

Question

我试图在我的网站上显示与 Facebook 服务器同步的可变时钟。Facebook 服务器时间位于: https://api.facebook.com/method/fql.query?query=SELECT+now%28%29+FROM+link_stat+WHERE+url+%3D+%271.2%27&format=json

如何在不刷新页面的情况下使其每秒变化？

Answer 1

假设有一些非书面函数，它应该看起来像这样:

var requestBegin = Date.now();
getServertimeFromFacebook(function callback(fbTime) {
    var requestEnd = Date.now();
    var latency = (requestEnd - requestBegin) / 2;
    var curDevicetime = Date.now(); // = requestEnd, of course
    var difference = fbTime - latency - curDeviceTime;

    function clock() {
        var cur = Date.now();
        var curFbTime = cur + difference;
        show(curFbTime); // print, log, whatever
    };
    setInterval(clock, …); // you could use a self-adjusting clock
                           // by using a setTimeout for each tick
});

你可以做

show = function(t) { console.log(new Date(t).toString()); };
getServertimeFromFacebook = function(cb) {
    ajax("https://api.facebook.com/method/fql.query?query=SELECT+now%28%29+FROM+link_stat+WHERE+url+%3D+%271.2%27&format=json", function(responsetext) {
         var obj = JSON.parse(responsetext);
         var ts = obj[0].anon,
             tms = ts * 1000;
         cb(tms);
    });
};