Javascript 如何使用 setInterval 和 clearInterval？
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How to use setInterval and clearInterval?
提问by Raj
function doKeyDown(event) {
switch (event.keyCode) {
case 32:
/* Space bar was pressed */
if (x == 4) {
setInterval(drawAll, 20);
}
else {
setInterval(drawAll, 20);
x += dx;
}
break;
}
}
Hi all,
大家好，
I want to call drawAll()oncenot creating a loopthat call drawAllagain and again, should I use recursive method for that or should I use clearInterval?
我想调用drawAll()一次而不是创建一个一次又一次调用的循环，drawAll我应该为此使用递归方法还是应该使用clearInterval？
Also please tell me to use clearInterval? Thanks :)
还请告诉我使用clearInterval？谢谢 ：）
回答by T.J. Crowder
setIntervalsets up a recurringtimer. It returns a handle that you can pass into clearIntervalto stop it from firing:
setInterval设置一个循环计时器。它返回一个句柄，您可以传入该句柄clearInterval以阻止其触发：
var handle = setInterval(drawAll, 20);
// When you want to cancel it:
clearInterval(handle);
handle = 0; // I just do this so I know I've cleared the interval
On browsers, the handle is guaranteed to be a number that isn't equal to 0; therefore, 0makes a handy flag value for "no timer set". (Other platforms may return other values; NodeJS's timer functions return an object, for instance.)
在浏览器上，句柄保证是一个不等于0;的数字。因此，0为“未设置计时器”设置一个方便的标志值。（其他平台可能会返回其他值；例如，NodeJS 的计时器函数会返回一个对象。）
To schedule a function to onlyfire once, use setTimeoutinstead. It won't keep firing. (It also returns a handle you can use to cancel it via clearTimeoutbefore it fires that one time if appropriate.)
要将函数安排为仅触发一次，请setTimeout改用。它不会继续射击。（clearTimeout如果合适，它还返回一个句柄，您可以在它触发一次之前用来取消它。）
setTimeout(drawAll, 20);
回答by Joshua - Pendo
clearIntervalis one option:
clearInterval是一种选择：
var interval = setInterval(doStuff, 2000); // 2000 ms = start after 2sec
function doStuff() {
alert('this is a 2 second warning');
clearInterval(interval);
}
回答by dlev
Use setTimeout(drawAll, 20)instead. That only executes the function once.
使用setTimeout(drawAll, 20)来代替。那只执行一次函数。
回答by PJ3
I used angular with electron,
我用角度和电子，
In my case, setIntervalreturns a Nodejs Timer object. which when I called clearInterval(timerobject)it did not work.
就我而言，setInterval返回一个 Nodejs Timer 对象。当我调用clearInterval(timerobject)它时它不起作用。
I had to get the id first and call to clearInterval
我必须先获取 id 并调用 clearInterval
clearInterval(timerobject._id)
clearInterval(timerobject._id)
I have struggled many hours with this. hope this helps.
我为此苦苦挣扎了好几个小时。希望这可以帮助。
回答by HynekS
Side note – if you want to use separate functions to set & clear interval, the interval variable have to be accessible for all of them, in 'relative global', or 'one level up' scope:
旁注 - 如果您想使用单独的函数来设置和清除间隔，则必须在“相对全局”或“上一级”范围内对所有函数都可以访问间隔变量：
var interval = null;
function startStuff(func, time) {
interval = setInterval(func, time);
}
function stopStuff() {
clearInterval(interval);
}
