Javascript 定时器延迟
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Javascript timer delay
提问by Katherine1
I've decided to play around with HTML5's canvas, and of course that means I'm going to try writing a pong game. At the moment, I am trying to figure out how to cap my framerate. This is fairly easy in other languages, but finding a way to delay execution in Javascript seems to be a bit tougher.
我决定尝试使用 HTML5 的画布，当然这意味着我将尝试编写乒乓球游戏。目前，我正试图弄清楚如何限制我的帧率。这在其他语言中相当容易，但在 Javascript 中找到一种延迟执行的方法似乎有点困难。
Here is what I have so far:
这是我到目前为止所拥有的：
while(true) {
var begin = (new Date()).getTime();
//Draw stuff to the canvas
var end = (new Date()).getTime();
if ((end-begin) < 33.333 ) {
//delay (1000/(30-(end-begin)))
}
}
Obviously, frame rates will be wildly different due to how each javascript engine performs, but I want to cap the maximum framerate at 30FPS. I don't really see how setTimeout() would accomplish this task. What would be the best way to do this?
显然，由于每个 javascript 引擎的执行方式，帧速率会大不相同，但我想将最大帧速率限制在 30FPS。我真的不明白 setTimeout() 将如何完成这项任务。什么是最好的方法来做到这一点？
回答by closure
There is no delay/ waitin JavaScript. You can use functions like window.setTimeoutto call a function after certain time has elapsed, example:
JavaScript 中没有delay/ wait。您可以使用函数window.setTimeout，例如在经过特定时间后调用函数，例如：
window.setTimeout(function() {
// do something interesting
}, 2000 /* but after 2000 ms */);
Or say you want to paint a frame every 33 ms (~30 fps), you will code it like:
或者说你想每 33 毫秒（~30 fps）绘制一个帧，你可以这样编码：
window.setInterval(function() {
// paint my frame
}, 33);
