Скачать или смотреть How to Solve the TypeError: Cannot read property 'data' of undefined in JavaScript

Learn how to effectively access objects within an array in JavaScript and solve common errors such as `TypeError: Cannot read property 'data' of undefined` in Google Apps Script.
---
This video is based on the question https://stackoverflow.com/q/68589824/ asked by the user 'GarrethTrent' ( https://stackoverflow.com/u/8327389/ ) and on the answer https://stackoverflow.com/a/68590039/ provided by the user 'lejlun' ( https://stackoverflow.com/u/14861737/ ) 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: Accessing object inside array in Javascript is returning TypeError: Cannot read property 'data' of undefined error

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.
---
How to Solve the TypeError: Cannot read property 'data' of undefined in JavaScript

Accessing data in JavaScript, particularly when it comes to arrays and objects, can sometimes lead to frustrating errors. One common issue developers face is the dreaded TypeError: Cannot read property 'data' of undefined. In this guide, we’ll explore a specific example of this error, understand why it occurs, and walk through a solution that ensures smooth data retrieval from JSON objects.

Understanding the Problem

In a recent scenario, a developer attempted to access elements in an array of objects, pulling values from a JSON response obtained from an API. The structure of the JSON is as follows:

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

The developer crafted the following code snippet to extract values:

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

However, this resulted in the error TypeError: Cannot read property 'data' of undefined when trying to access specific array elements. Let's break down the solution to rectify this.

Breaking Down the Solution

To overcome this error, we will follow these steps:

Iterate Over the Array: We'll loop through the JSON object to effectively access each entry.

Access the Data Safely: Rather than directly accessing the first index (e.g., [0]), we'll ensure that the arrays we want to access indeed have data before attempting to pull it.

Construct a New Object: Gather the desired properties into a new object for each item processed.

Full Code Implementation

Here’s how you can implement this solution in a more robust manner:

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

What the Code Does

The code initializes a received array containing JSON objects.

It iterates through each object using a for loop.

For each object, it constructs a new object (newObj) using reduce() that pulls out the data values safely by checking array lengths.

Finally, it pushes the constructed object into allValues, which can be logged or used elsewhere in your application.

Conclusion

Errors like TypeError: Cannot read property 'data' of undefined can be common when handling nested arrays and objects in JavaScript. By following clear logic in our code and ensuring we safely access data, we can avoid these pitfalls and effectively manipulate the data we receive from APIs.

If you find yourself in a similar situation, try implementing the solution outlined here. Happy coding!