Скачать или смотреть Fixing the Vue.js Error: Cannot read properties of null when Displaying Array Elements

Learn how to resolve the "Cannot read properties of null" error in Vue.js when trying to access elements from an API-driven associative array.
---
This video is based on the question https://stackoverflow.com/q/77768378/ asked by the user 'Jean-Loup' ( https://stackoverflow.com/u/5427882/ ) and on the answer https://stackoverflow.com/a/77768462/ provided by the user 'Jean-Loup' ( https://stackoverflow.com/u/5427882/ ) 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, comments, revision history etc. For example, the original title of the Question was: Vuejs template : "Cannot read properties of null" but Array is defined

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 Fix the Vue.js Error: Cannot read properties of null When Accessing Array Elements

In Vue.js, handling data from APIs is quite common. However, sometimes developers encounter frustrating issues, such as the infamous error: Cannot read properties of null. In this post, we'll explore a common scenario where this error occurs and how to resolve it effectively.

The Problem

Imagine you're trying to display elements from an associative array that you've fetched from an API in your Vue.js application. Initially, you set a data property, info, to null and then, after fetching and formatting the data, you aim to access a specific property from it in your template like so:

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

However, doing this results in the following error:

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

You may find yourself confused because printing the entire info object, using {{ this.info }}, shows that it is indeed defined with the correct data.

Why This Happens

This error occurs due to how the initial state of the info variable is defined. When the component is mounted, info is set to null, and attempting to access any property (like name) on null leads to a TypeError. The Vue.js template tries to render this data before the asynchronous call to fetch data completes.

The Solution

The solution to this problem is fairly straightforward. Instead of initializing the info variable to null, initialize it as an empty object. Here’s how to do this:

Step 1: Adjust Your Data Initialization

Replace your initial state declaration from this:

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

To this:

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

Step 2: Understand the Impact

By initializing info as an empty object instead of null, your template can safely attempt to access properties without throwing errors. This ensures that when Vue.js renders your template, it attempts to read {{ this.info.name }} and doesn’t encounter a null reference error.

Step 3: Fetching Data

When you fetch data from your API and subsequently format it, you can still easily update info as required:

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

Conclusion

By simply changing the initial value of the info variable from null to an empty object, you can prevent Vue.js from throwing the Cannot read properties of null error. This small adjustment can save time and prevent confusion as you continue to build and debug your Vue.js applications.

Final Notes

Remember, in Vue.js or any reactive framework, initializing your state properly is crucial to prevent runtime errors. Make these adjustments, and you'll find smooth sailing as you work with arrays and object properties in your templates!