How to Convert a `setTimeout` Callback into a Promise?

How to Create a Promise from setTimeout

The Problem:

In asynchronous programming, it can be beneficial to convert callbacks into promises. However, a non-promise-based function like setTimeout does not immediately return a promise by default. This article explores how to create a promise that can be used within the context of a function like setTimeout.

Initial Thoughts:

The provided example defines a setTimeout function with a callback. To create a promise, it is necessary to wrap the setTimeout callback within the promise constructor's executor function.

Revised Solution:

Using modern JavaScript and Promises, the following code demonstrates how to create a promise from setTimeout:

function later(delay) {
  return new Promise(resolve => setTimeout(resolve, delay));
}

This later function takes a delay and returns a promise that resolves after the specified delay. You can then use the returned promise in your asynchronous code.

Advanced Considerations:

For more advanced scenarios, consider the following variations of the later function:

• Delayed Promise with Value: You can pass a value to the setTimeout callback, which will be resolved by the promise.
• Cancellable Promise: To cancel the setTimeout and the associated promise, you can create an object that includes a cancel method.

Conclusion:

Creating promises from callbacks like setTimeout allows for easier integration of asynchronous operations into your codebase. By understanding how to implement this technique, you can improve the readability and maintainability of your asynchronous JavaScript applications.

The above is the detailed content of How to Convert a `setTimeout` Callback into a Promise?. For more information, please follow other related articles on the PHP Chinese website!