Скачать или смотреть How to Use the Result of a fetch Call in a For Loop of Fetch Calls in JavaScript

Learn how to effectively manage multiple `fetch` calls in JavaScript using async/await to retrieve additional data from APIs like Google Maps.
---
This video is based on the question https://stackoverflow.com/q/75611973/ asked by the user 'Josh Watkins' ( https://stackoverflow.com/u/21316618/ ) and on the answer https://stackoverflow.com/a/75612057/ provided by the user 'Brightness0302' ( https://stackoverflow.com/u/21294859/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: How to use the result of a fetch call in a for loop of fetch calls in JS?

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Handling Multiple Fetch Calls in JavaScript

When working with APIs, especially in a context like the Google Maps API, you might often find yourself needing to make several fetch calls to gather all the desired data. If you're a newcomer to JavaScript, the asynchronous nature of API calls may seem overwhelming, especially when using fetch within loops. In this post, we'll explore how to efficiently manage multiple fetch calls in a for loop, utilizing JavaScript's async/await syntax.

The Problem: Retrieving Additional Location Data

Imagine you're creating an application that allows users to search for nearby locations. You successfully make a call to the Google Maps API and retrieve a list of relevant places. However, the data you receive lacks essential details, such as phone numbers and website links. Fortunately, each response includes a place ID, which you can use to make a second fetch call to gather the additional information you need.

Here's a simplified version of what you might initially try:

[[See Video to Reveal this Text or Code Snippet]]

However, the above code won't yield the desired results due to the synchronous nature of JavaScript, which can lead to Promise issues when calling asynchronous functions like fetch in a for loop.

The Solution: Using Async/Await

To effectively manage multiple asynchronous operations, we can use the async/await pattern. This enables us to write cleaner and more readable asynchronous code. Here's how you can rewrite the above code using async/await:

Step 1: Declare Your Asynchronous Function

First, you'll need to declare an async function to allow the use of await inside it:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Fetch the Initial Data

In this example, we are using await with the initial fetch call. This ensures that we first receive the data before trying to access individual results.

Step 3: Fetch Additional Data in the Loop

Within the loop, we again use await to get the details for each specific place using the place ID. This eliminates the callback hell you may have experienced with nested then calls and keeps your code clean and easy to follow.

Alternative: Using Promise.all

If you have a large number of fetch calls and want to run them in parallel rather than sequentially (which can be more efficient), you can use Promise.all instead. Here's how this looks:

[[See Video to Reveal this Text or Code Snippet]]

This version will fire off all the additional fetch calls simultaneously, allowing you to handle many responses at once, which can significantly improve performance if network conditions permit.

Conclusion

Using async/await simplifies the syntax and allows for a more manageable approach when dealing with multiple fetch calls in JavaScript. Whether you choose to process each fetch sequentially or in parallel with Promise.all, understanding these patterns will help you effectively interact with APIs like Google Maps and enhance your application's functionality. Happy coding!