You might see the need to wait for a short period before you do a certain action from time to time. JavaScript has setTimeout for this, and it works perfectly fine. But what if you want to work with Promises and perhaps even async/await?
setTimeout breaks this pattern because it takes a callback. But gladly, we can combine both to create a delayed Promise you can await if you want.
The Code
const delay = (delay, value) => {
let timeout;
let _reject;
const promise = new Promise((resolve, reject) => {
_reject = reject;
timeout = setTimeout(resolve, delay, value);
});
return {
promise,
cancel() {
if (timeout) {
clearTimeout(timeout);
timeout = null;
_reject();
_reject = null;
}
}
};
};Usage
You can then use it like this afterward:
const delayed = delay(5000, "This value is returned by the promise"); // This await only returns after at least 5 seconds. // Execution is halted before it continues after the // Promise resolves. const value = await delayed.promise; // more operations...
And if you want to take advantage of being able to cancel it, you can use it like this:
const delayed = delay(5000, "value");
delayed.promise
.then((value) => console.log(value))
.catch(() => console.error("Rejected"));
// This will be executed before the promise fires.
// Thus, the Promise is canceled and
// the catch is executed.
delayed.cancel();The Whole Tip As An Image
If you like visual content more, or if you want to store it for later, I put all this into one single image for you. I hope you like it!
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