Скачать или смотреть Fixing the undefined Issue in Fetch API Responses

Learn how to resolve the `undefined` problem when using Fetch API and Promises in JavaScript. Enhance your web app development skills with this straightforward solution!
---
This video is based on the question https://stackoverflow.com/q/62938725/ asked by the user 'ETHan' ( https://stackoverflow.com/u/11968952/ ) and on the answer https://stackoverflow.com/a/62938871/ provided by the user 'Selven' ( https://stackoverflow.com/u/759013/ ) 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: Using a promise with Fetch API response still has my data returning as undefined

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.
---
Fixing the undefined Issue in Fetch API Responses: A Simple Guide

If you’ve ever been building a web application using JavaScript and the Fetch API, you might have encountered the frustrating issue of receiving undefined when trying to access data. This issue commonly arises when handling asynchronous operations and promises. In this guide, we’ll dive deep into a specific scenario where this happens and walk through a clear solution.

The Problem

You’re creating a web app that lets users search for video game player statistics. In your code, you’re using the Fetch API to get data from a URL. However, when you try logging the fetched data or pushing it into an array, you’re left with undefined. Here’s a simplified description of the initial code:

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

The goal here is to log the data returned by the Fetch API and store it within the player array. So why doesn't your code work as expected?

Understanding the Issue

Why Is My Data undefined?

Return Value Handling: In promises, every .then() method needs to return a value that can be used in the next step of the chain. If you don’t return the data in the final .then(), nothing can flow from there to subsequent code.

Incorrect Usage of push: The way you’re trying to push data into the player array is also incorrect. You are using playerData.push(player);, which is not how you should be doing it. Remember, playerData is meant to hold the fetched response, which you actually want to add to player, not the other way around.

The Solution

Let’s make the necessary changes to ensure you receive the right data and push it into the player array correctly. Here’s an updated version of the code:

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

Key Changes Made:

Returning Data: In the .then((data) => {...}), I included return data; to make sure the fetched data is carried over to the next .then() call.

Fixed push: I changed playerData.push(player); to player.push(playerData); so that the fetched data gets added to the correct array.

Conclusion

Working with promises and async operations can be tricky, especially when fetching data from an API. By ensuring that you return values correctly and handle your data appropriately, you can avoid the common pitfall of receiving undefined. This small but crucial understanding can significantly enhance your skills in JavaScript and improve your web app functionalities.

If you have further questions or need clarification on fetch API usage, feel free to ask in the comments below! Happy coding!