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Learn how to manage TypeScript type checking for React component props effectively by extending types and ensuring compatibility with `AxiosInstance`.
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How to Successfully Pass TS Type Checking for Component Props in React

TypeScript is a powerful tool for enhancing JavaScript applications, particularly when it comes to providing type safety in React components. One common challenge developers face is ensuring that all the props passed to a component are correctly typed. If you're wondering about how to pass TypeScript type checking for component props when there's a mix of custom props, you’re not alone!

In this post, we'll take a closer look at how to effectively manage prop types in React components using TypeScript, along with a specific case involving AxiosInstance props.

The Challenge

Imagine you have a React functional component, and you've defined a set of props through an interface called SpaProps. They include properties a, b, and c. However, you also want to add another property d, which is of type AxiosInstance, but the original SpaProps does not account for it. Here’s an example of the component definition:

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Here lies the problem: the property d does not belong to SpaProps. This can lead to TypeScript throwing an error since it cannot match the expected prop types. How can we solve this issue while ensuring that our component remains type-safe and compliant with TypeScript’s strict typing system?

The Solution: Extending Prop Types

To solve the problem, you can extend the prop types in TypeScript. This allows you to combine existing types with new ones, so you include all the properties you need seamlessly.

Step 1: Define the New Interface

First, we need an interface that defines the new property we want to add:

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With this interface, d is now defined and we can proceed to extend our existing prop types.

Step 2: Combine the Interfaces

You would then combine this new interface with SpaProps using an intersection type. Here’s how you can do that:

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This line effectively tells TypeScript that Component will accept props that conform to both SpaProps and IT, meaning a, b, c, and d are all accounted for.

Alternative: Directly Defining Props

If you are unsure of the type for d but you still want to include it, you can also redefine your component props directly with an inline type:

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This approach is handy if the specific type of d is not clearly defined yet or may change in the future.

Recap and Best Practices

Using TypeScripts’ ability to extend interfaces allows for:

Prop Safety: Ensures that the parameters expected by your components are strictly enforced.

Maintainability: Easier to add or modify prop types down the road, without needing to refactor much code.

Clarity: Clearly stating which props your component expects helps both in development and for future coders looking at your code.

Key Takeaways:

Use interface extensions to combine props.

Maintain type safety while handling components that have varying prop types.

When in doubt, define props inline to keep typing flexible.

By following these steps, you can ensure that your TypeScript type checking passes successfully, giving you the confidence to build robust React components. Happy coding!