blocks|key|5420897|text|您提出的方法不起作用，因为Javascript+(主要)是单线程的-循环在无限循环中开始，所以setTimeout处理程序永远不会被调用，所以keepGoing永远不会被设置，所以循环无法结束。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|5420898|最简单的方法是确定函数结束的绝对时间，并且每隔一段时间(即不是在每次迭代时)检查当前时间是否已超过该时间点。|5420899|选择一些迭代，使您在已用时间的测试效率和您准备让函数具有的“超时”量之间达到一个合理的折衷。|5420900|entityMap^0|1B|A|1Z|9|0|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@$9|M|A|N|B|C]|$9|O|A|P|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Q|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|R|8|@]|D|@]|E|$]]|$1|J|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|K|$]]

Your proposed method doesn't work because Javascript is (mostly) single threaded - the loop starts off in an infinite loop, so the <code>setTimeout</code> handler never gets invoked, so <code>keepGoing</code> never gets set, so the loop can't finish.

It would be simplest to determine an absolute time at which the function is to finish, and every so often (i.e. not on every iteration) check whether the current time has passed that point.

Pick a number of iterations that gives you a reasonable compromise between the efficiency of the test for elapsed time, and the amount of "overtime" you're prepared to let the function have.

blocks|key|5420910|text|Count开始一个无限循环，您的代码永远不会到达setTimeout()。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5420911|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Count begins an endless loop, your code never reaches the setTimeout().

blocks|key|5903217|text|三个问题：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5903218|5903219|您的超时设置为在一次回调中触发setTimeout将达不到，因为count永远不会结束|unordered-list-item|offset|length|style|CODE|5903220|您的alert应在while之后从count内部调用，或从setTimeout回调中调用。|5903221|5903222|解决这些问题，你的代码就应该可以工作了。尽管如此，我可能会提前设置一个结束日期，并与while中的日期进行比较。|5903223|entityMap^0|0|0|F|A|W|5|0|2|5|9|5|H|5|T|A|0|0|16|5|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|R|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|S|8|@$F|T|G|U|H|I]|$F|V|G|W|H|I]]|9|@]|A|$]]|$1|J|3|K|5|E|7|X|8|@$F|Y|G|Z|H|I]|$F|10|G|11|H|I]|$F|12|G|13|H|I]|$F|14|G|15|H|I]]|9|@]|A|$]]|$1|L|3|-4|5|6|7|16|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|17|8|@$F|18|G|19|H|I]]|9|@]|A|$]]|$1|O|3|-4|5|6|7|1A|8|@]|9|@]|A|$]]]|P|$]]

Three issues:

<ul>
<li>Your timeout is set to fire in one millisecond</li>
<li>Your <code>setTimeout</code> will not be reached because <code>count</code> will never finish</li>
<li>Your <code>alert</code> should be called from within <code>count</code> after the <code>while</code>, or from within the <code>setTimeout</code> callback.</li>
</ul>

Address those issues and your code should work. Still, I might have gone with setting an end date up front, and comparing with that date in the <code>while</code>.

blocks|key|5420987|text|我不知道目的是什么，但你得打断一下|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5420988|function+count()+{
++++while(keepGoing)+{
++++++++i+=+i%2B1;
++++}
}|code-block|syntax|javascript|5420989|一段时间，让keepGoing有机会在其他同时运行的地方更改。另外，你永远不会这样做：|offset|length|style|CODE|5420990|while(keepGoing)+{
++++i+=+i%2B1;
}|5420991|你完全阻塞了everything的线程...您必须将函数的工作分成小块，并使用setTimeout或setInterval以小批方式运行它，如下所示，同时接近您可能想要的：|BOLD|5420992|var+piece_n=0;
var+keepGoing+=+true;+
var+interval_id+=+setInterval(function+()+{
++++if(keepGoing){
++++++++//do_a_short_piece_of_work(piece_n);
++++++++piece_n%2B%2B;
++++}else{
++++++++clearInterval(interval_id);
++++}
},500);+//ticking+every+half+second

setTimeout(function+()+{+keepGoing+=+false;+},+10000);+//run+for+a+small+bit+more+than+10+to+10.5+seconds+%2B+do_a_short_piece_of_work()+execution+time|5420993|如果你只需要10秒而不会饿到剩下的时间，你将需要调整一系列的setTimeout，并且你需要提前知道一点(比下一个滴答多一点)，这样你就可以在准确的时间设置最后一个setTimeout+(参考当前日期和保存的初始日期)。一切都可以分成更小的块，就像cpu的指令一样:)|5420994|entityMap^0|0|0|6|9|0|0|6|A|0|0|0^^$0|@$1|2|3|4|5|6|7|X|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|Y|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Z|8|@$I|10|J|11|K|L]]|9|@]|A|$]]|$1|M|3|N|5|D|7|12|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|13|8|@$I|14|J|15|K|Q]]|9|@]|A|$]]|$1|R|3|S|5|D|7|16|8|@]|9|@]|A|$E|F]]|$1|T|3|U|5|6|7|17|8|@]|9|@]|A|$]]|$1|V|3|-4|5|6|7|18|8|@]|9|@]|A|$]]]|W|$]]

I don't know what is the purpose but you would have to interrupt

<pre><code>function count() {
 while(keepGoing) {
 i = i+1;
 }
}
</code></pre>

for a while to give a chance for <code>keepGoing</code> to change in some other place that runs meanwhile. Also you never do this:

<pre><code>while(keepGoing) {
 i = i+1;
}
</code></pre>

You are completely blocking the thread for everything...
You will have to divide your function's work into small pieces and use setTimeout or setInterval to run it in small batches, something like the following, while close to what you may want:

<pre><code>var piece_n=0;
var keepGoing = true; 
var interval_id = setInterval(function () {
 if(keepGoing){
 //do_a_short_piece_of_work(piece_n);
 piece_n++;
 }else{
 clearInterval(interval_id);
 }
},500); //ticking every half second

setTimeout(function () { keepGoing = false; }, 10000); //run for a small bit more than 10 to 10.5 seconds + do_a_short_piece_of_work() execution time
</code></pre>

If you need exactly 10 seconds without starving the rest you will need to adjust in a series of setTimeout and you will need to know a bit in advance (more than next tick) so you can set the last setTimeout at the exact time (consulting current date and saved initial date).
Everything can be divided into smaller chunks, like instructions for a cpu :)

I need to let a function run for a fixed number of seconds, then terminate. I could use jQuery or web workers, but my attempt at doing it directly faild. 

Tks for help this now works:

<pre><code>startT = new Date().getTime();
i = 1;

while(true){
 now = new Date().getTime();
 if( (now - startT) &gt; 100) {
 break;
 } 

 i++;
}

alert(i);
</code></pre>

Stop execution of function after fixed time in javascript

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我需要让一个函数运行固定的秒数，然后终止。我可以使用jQuery或web workers，但我直接尝试这样做的尝试失败了。Tks的帮助现在起作用了：startT = new Date().getTime();i = 1;while(true){    now = new Date().getTime();    if( (now - startT) > 100) {        break;  

问在javascript中的固定时间后停止函数的执行
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