How to use setInterval and clearInterval?

How to use setInterval and clearInterval?

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,
I want to call drawAll() once not creating a loop that call drawAll again and again, should I use recursive method for that or should I use clearInterval?
Also please tell me to use clearInterval? Thanks 🙂

Solutions/Answers:

Solution 1:

setInterval sets up a recurring timer. It returns a handle that you can pass into clearInterval to stop it from firing:

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, 0 makes a handy flag value for “no timer set”. (Other platforms may return other values; NodeJS’s timer functions return an object, for instance.)

To schedule a function to only fire once, use setTimeout instead. It won’t keep firing. (It also returns a handle you can use to cancel it via clearTimeout before it fires that one time if appropriate.)

setTimeout(drawAll, 20);

Solution 2:

clearInterval is one option:

var interval = setInterval(doStuff, 2000); // 2000 ms = start after 2sec 
function doStuff() {
  alert('this is a 2 second warning');
  clearInterval(interval);
}

Solution 3:

Use setTimeout(drawAll, 20) instead. That only executes the function once.

Solution 4:

I used angular with electron,

In my case, setInterval returns a Nodejs Timer object. which when I called clearInterval(timerobject) it did not work.

I had to get the id first and call to clearInterval

clearInterval(timerobject._id)

I have struggled many hours with this. hope this helps.

Solution 5:

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:

var interval = null;    

function startStuff(func, time) {
    interval = setInterval(func, time);
}

function stopStuff() {
    clearInterval(interval);
}