为什么 JS 模态消息框会在 setTimeout() 上暂停倒计时?

I expected setTimeout(fn,10000) to mean "check current time periodically and when it is greater than Now + 10000ms fire the event handler that will invoke the passed 'fn' function". This would be logical, seeing how we pass the timeout measure as 'ms from now'. But, apparently, the countdown on setTimeout is a literal countdown and will be paused while a modal window is open.

setTimeout(function(){
    //alert A
    alert("10 seconds have passed for the first setTimeout")
}, 10000);
setTimeout(function(){
    //alert B
    alert("Wait for 15 seconds and press OK");
},1000);

我希望警报 A 在您关闭警报 B 后立即显示(假设您等待了 15 秒)，因为警报 A 超时仅 10 秒并且它们已经过去了.然而，实践表明，警报 A 的倒计时只是在警报 B 打开时暂停，并且仅在大约 10 分钟后才会显示.关闭警报 B 后又过了 9 秒，无论 B 打开了多长时间.