超时未按预期工作

首先,我英语说得不太好。 但我想帮你

如果第一个任务正在运行,则将保留所有事件

您声明了setTimeout 但是,此setTimeout在0.5s内运行

因为whileloop在单线程浏览器中只有一个线程

Wrestling with the Browser Event Queue

Concurrency model and Event Loop

以下是可视化运行上述代码时发生的事情的最佳方法:

http://latentflip.com/loupe/?code=Y29uc29sZS50aW1lKCJUaW1lIik7DQp2YXIgaT0wOw0Kc2V0VGltZW91dChmdW5jdGlvbigpe2NvbnNvbGUubG9nKCJUaW1lb3V0Li4uIil9LDUwMCk7DQoNCndoaWxlKHRydWUpew0KICBpZihpPT0xMDAwMDAwMDAwKXsNCiAgICBjb25zb2xlLnRpbWVFbmQoIlRpbWUiKTsNCiAgICBjb25zb2xlLmxvZygid2hpbGVsb29wIGJyZWFraW5nLi4uIik7DQogICAgYnJlYWs7DQogIH0NCiAgZWxzZXtpKys7fQ0KfQ0KIA%3D%3D!!!PGJ1dHRvbj5DbGljayBtZSE8L2J1dHRvbj4%3D

    console.time("Time");
        var i=0;
        //here a callback is registered and should be called when timer expires
        setTimeout(function(){console.log("Timeout...")},500);

        //since settimeout is async in nature, main thread continues 
    //to execute new line of code i.e. while loop
        // After 500 ms when timer expires, it puts the callback in event queue, 
    // the callback will be executed as soon as it sees the main thread free, but since 
//while loop is running on main thread for 2sec, the main thread will be free //only after 2 sec (or while loop) finishes.
        while(true){
          if(i==1000000000){
            console.timeEnd("Time");
            console.log("whileloop breaking...");
            break;
          }
          else{i++;}
        }
        // as there is no code to be executed now, main thread takes new task from 
        // event Queue, in this case the new task is callback from settimeout.

我希望这能帮助你了解一点关于settimeout的内容

但是如果你想打印 暂停 首先,然后 同时断开回路 在你的代码中,然后试试这个--

console.time("Time");
var i=0;
//setTimeout(function(){console.log("Timeout...")},500);
setTimeout(console.log("Timeout..."),500);

while(true){
  if(i==1000000000){
    console.timeEnd("Time");
    console.log("whileloop breaking...");
    break;
  }
  else{i++;}
}

我刚搬走 function(){} setTimeout ..