NodeJS
When and Why to Use Promise.race() in JavaScript
Introduction
Asynchronous operations are a standard part of web development in JavaScript. While Promise. Promise.all() is used to run multiple promises in parallel and wait until all of them resolves. race() behaves differently. It is useful for cases in which you only care about the first promise that either resolves or rejects.
What is Promise.race()?
Promise. race(): If you want to wait for the first promise to settle (either resolve or reject), you can use Promise.race(). This is especially valuable for implementing a "race" condition, where you wish to act on whichever promise resolves first.
Real-World Example
For example, when making an API request we might be interested in canceling it or displaying a timeout message, if it takes too long. This is where Promise.race() shines.
const apiRequest = fetch('https://api.example.com/data').then(res => res.json());const timeout = new Promise((_, reject) => setTimeout(() => reject('Request timed out'), 5000));Promise.race([apiRequest, timeout]) .then(data => console.log('Data:', data)) .catch(error => console.log('Error:', error));In this example, when the fetch request is completed before the timeout, it resolves the data. But if the timeout (5 seconds) is hit first, it rejects with a Request timed out error. Promise.race() ensures you don’t wait longer than the defined time.
When to Use Promise.race()
Timeout: To restrict the absolute wait time to wait for an async operation. Something like a network request or user input.
Race Conditions: Native, First and Finish Operations For instance, fetching data in parallel from multiple sources and responding as soon as the first response comes in.
Fail-fast Logic: In cases where you have to reject and abort other promises as soon as one of your promises fails.
Advantages of Promise.race()
Improved Error Handling: Error handled at once enables you to respond as soon as one of the promises resolves or gets rejected, therefore is good for time-sensitive task
Better Performance: It avoids waiting for every promise to resolve if you are only interested in the first one that completes.
When to Use Promise.race()
Improved Error Handling: Error handled at once enables you to respond as soon as one of the promises resolves or gets rejected, therefore is good for time-sensitive task
Better Performance: It avoids waiting for every promise to resolve if you are only interested in the first one that completes.
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