Скачать или смотреть Understanding Why the Arrow Operator Doesn't Return a Function in JavaScript

A detailed guide on resolving the `TypeError` in JavaScript related to the arrow operator not returning a function. Learn how to effectively use `apiClient` with proper parameter handling.
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Understanding the TypeError with the Arrow Operator in JavaScript

If you're working with modern JavaScript (ES6) and are relatively new to some of its conventions, you might encounter a few hiccups, especially when working with arrow functions and API clients. One common issue is when you try to use an arrow operator to create a client function, but instead, you receive an error stating: TypeError: _client.apiClient.get is not a function. In this guide, we'll dive deep into the reasons behind this issue and how to resolve it effectively.

What Works?

In the following example, everything works perfectly because apiClient is defined using the create function from the apisauce library, which returns an object that has a get method.

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

When imported in another file, it allows you to make API calls efficiently:

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This works without any errors because apiClient is an object, and you can simply call the get method on it.

Understanding the Problem

However, trouble arises when you try to modify apiClient into an arrow function intending to pass a parameter. Here's a look at the code that leads to the error:

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

In this case, apiClient is now a function, and when you try calling apiClient.get(endpoint), JavaScript throws a TypeError because apiClient doesn't refer to an object with a get method anymore.

Why Does This Happen?

In this modified version of apiClient, the arrow function only returns the value of create, but it does not store it or return it properly. Therefore, when you try to access get from apiClient, it results in an error, because apiClient does not return an object to use that method on. This can be shown through these variations:

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or

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Both have the same issue, as they return a function, not the apiClient instance with the desired methods.

The Solution

To fix this issue and make apiClient a fully functional and usable API client, you can modify your calling approach. You simply need to invoke the apiClient() function to retrieve the object created by create. You can do it in two ways:

Solution A: Calling apiClient Without Parameters

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Solution B: Calling apiClient With Parameters

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

This approach effectively retrieves the necessary object with the get method, allowing you to perform your API calls smoothly.

Conclusion

JavaScript's arrow functions provide powerful options for function declaration, but they come with nuances that can lead to unexpected issues. Understanding how to properly return and use objects is key to efficiently handle API clients using ES6 syntax. By following the solutions outlined in this post, you should be able to overcome the TypeError and use your API client as intended. Happy coding!