如何修复JavaScript中的settimeout内存泄漏问题

Question

I have a JS function like this

function check() {
    ...do something
}

Now, I want to run it when script start, and at start of everyday (00:00:01 everyday). My code now look like this

function check() {
    ...do something

    let today = new Date();
    let tomorrow = new Date();
        tomorrow.setHours(0,0,1,0);
        tomorrow.setDate(tomorrow.getDate()+1);

    console.log("next check in", tomorrow-today);
    setTimeout(() => { check() }, tomorrow-today);
}
check();

I'm using setTimeout inside check(). I think it's bad code because it will create a loop, and function check() will never been cleanup. How to fix it ?

Answer 1

You are right that uncontrolled recursion could cause exhaustion of resources due to the stack growing indefinitely. For example, the following Javascript program will crash after check() is executed sufficient times without first return ing:

function check() {
  check();
}
check();

The following code will not crash in this way:

function check() {
  setTimeout(check, 1000);
}
check();

This code can run indefinitely without exhausting the stack because each time check() is run, it is allowed to run to completion and return before it is run in the future.

This works because the setTimeout() function doesn't directly run check() . Instead, it tells the Javascript runtime to schedule an execution of check() for 1s into the future. When it and check() have completed, the Javascript stack becomes empty. 1s later, the execution of check() is queued and eventually executed as long as the Javascript stack is clear.

Since the Javascript stack must be clear before check() can run, stack overflows are avoided.

Answer 2

You could add the function clearTimeout(timer):

let timer = setTimeout(() => check());

clearTimeout(timer);