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Added details about setTimeout() and setInterval() returns a Timeout … #7759

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12 changes: 10 additions & 2 deletions apps/site/pages/en/learn/asynchronous-work/discover-javascript-timers.md
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Original file line number Diff line number Diff line change
Expand Up @@ -33,7 +33,7 @@ const myFunction = (firstParam, secondParam) => {
setTimeout(myFunction, 2000, firstParam, secondParam);
```

`setTimeout` returns the timer id. This is generally not used, but you can store this id, and clear it if you want to delete this scheduled function execution:
`setTimeout` returns a timer identifier. In Node.js, this is a Timeout object that provides additional functionality, while in browsers it returns a numeric ID. You can store this identifier and use it to cancel the scheduled function execution:
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`setTimeout` returns a timer identifier. In Node.js, this is a Timeout object that provides additional functionality, while in browsers it returns a numeric ID. You can store this identifier and use it to cancel the scheduled function execution:
`setTimeout` returns a [`Timeout`](https://nodejs.org/api/timers.html#class-timeout) instance in Node.js, whereas in browsers it returns a numeric ID. This object or ID can be used to cancel the scheduled function execution:


```js
const id = setTimeout(() => {
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These example should probably not use id, they are meant for Node.js, so let's use a more specific variable name

Suggested change
const id = setTimeout(() => {
const timeout = setTimeout(() => {

Expand All @@ -44,6 +44,12 @@ const id = setTimeout(() => {
clearTimeout(id);
```

In Node.js, the Timeout object provides additional methods:

- `timeout.ref()`: Keeps the Node.js event loop active while the timer is running
- `timeout.unref()`: Allows the Node.js event loop to exit even if the timer is still running
- `timeout.refresh()`: Resets the timer's start time to the current time

Comment on lines +47 to +52
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In Node.js, the Timeout object provides additional methods:
- `timeout.ref()`: Keeps the Node.js event loop active while the timer is running
- `timeout.unref()`: Allows the Node.js event loop to exit even if the timer is still running
- `timeout.refresh()`: Resets the timer's start time to the current time

See my other suggestion. We can link to the documentation.

### Zero delay

If you specify the timeout delay to `0`, the callback function will be executed as soon as possible, but after the current function execution:
Expand Down Expand Up @@ -87,6 +93,8 @@ const id = setInterval(() => {
clearInterval(id);
```

Like `setTimeout`, `setInterval` returns a Timeout object in Node.js (and a numeric ID in browsers). This object provides the same additional methods (`ref()`, `unref()`, and `refresh()`).

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Like `setTimeout`, `setInterval` returns a Timeout object in Node.js (and a numeric ID in browsers). This object provides the same additional methods (`ref()`, `unref()`, and `refresh()`).

Earlier, we say "setInterval is a function similar to setTimeout", which I think implies they have the same return.

It's common to call `clearInterval` inside the setInterval callback function, to let it auto-determine if it should run again or stop. For example this code runs something unless App.somethingIWait has the value `arrived`:

```js
Expand Down Expand Up @@ -130,6 +138,6 @@ to achieve this scenario:

![Recursive setTimeout](/static/images/learn/javascript-timers/recursive-settimeout.png)

`setTimeout` and `setInterval` are available in Node.js, through the [Timers module](https://nodejs.org/api/timers.html).
`setTimeout` and `setInterval` are available in Node.js, through the [Timers module](https://nodejs.org/api/timers.html). In Node.js, these functions return a Timeout object that provides additional functionality for timer management.
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`setTimeout` and `setInterval` are available in Node.js, through the [Timers module](https://nodejs.org/api/timers.html). In Node.js, these functions return a Timeout object that provides additional functionality for timer management.
`setTimeout` and `setInterval` are available in Node.js, through the [Timers module](https://nodejs.org/api/timers.html).

We've already said this earlier in the document.


Node.js also provides `setImmediate()`, which is equivalent to using `setTimeout(() => {}, 0)`, mostly used to work with the Node.js Event Loop.