How to Fix the Cannot read property 'get' of undefined Error When Using Axios in React Hooks

Learn how to resolve the issue of an undefined Axios instance in React hooks and ensure a smooth data loading experience.
---

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: Axios instance in React hook "Cannot read property 'get' of undefined"

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Dealing with Axios Instance Errors in React Hooks

When working with React and Axios for making HTTP requests, you may come across errors that disrupt the flow of your application. One such frustrating error is: Cannot read property 'get' of undefined. This can be particularly puzzling, especially when your branches of data seem to load correctly. In this post, we'll explore why this error occurs and how to fix it effectively.

Understanding the Problem

The error arises in your application when trying to call the get method on an Axios instance that is not defined at the moment of execution. This often happens when your Axios setup is asynchronous, causing your components to render before the Axios instance is fully initialized.

Here’s what happens in your code:

You create an Axios instance in a custom hook (useAxios).

The hook returns the Axios instance once it is set up.

How to Fix the Error

To avoid this Cannot read property 'get' of undefined error, we can tweak the implementation of the Registration component to ensure the Axios instance is defined before calling its methods. Let’s break down the steps needed to achieve this.

Modified Registration Component

Here’s the corrected implementation:

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

Key Changes Explained

Conditional Check: In the useEffect hook, we modified the logic to ensure that the loadBranches function is only invoked when axiosInstance is defined. The expression axiosInstance && loadBranches() guarantees that we don’t call the function unless the Axios instance is available.

Understanding Dependency Arrays in useEffect

You may also have noticed that trying to run loadBranches without including it in the dependency array of useEffect results in a warning. React verifies every dependency for potential state updates, and not including all dependencies may lead to stale closures.

When defining the dependency array for useEffect, keep in mind:

Include all dependencies that your function uses that could change. This avoids issues with stale data and ensures reactively correct behavior.

Use empty arrays ([]) cautiously: An empty dependency array indicates that the effect should run only on mount, which can be problematic if any of the values it depends on change (for example, if you want to re-fetch data after a token is updated).

Conclusion

By ensuring that your Axios instance is ready before making requests and understanding the use of dependency arrays in React hooks, you can eliminate the dreaded Cannot read property 'get' of undefined error and build resilient applications.

Remember, robust error handling and state management are key to creating smooth user experiences in your applications. Happy coding!