Скачать или смотреть Extending Express Request Body with TypeScript

Learn how to effectively declare the request body type in Express.js with TypeScript, ensuring better type safety and enhanced code clarity.
---
This video is based on the question https://stackoverflow.com/q/66418176/ asked by the user 'T THE R' ( https://stackoverflow.com/u/14177036/ ) and on the answer https://stackoverflow.com/a/66419101/ provided by the user 'hoangdv' ( https://stackoverflow.com/u/5196394/ ) 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: Typescript extends Express Request body

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.
---
Extending Express Request Body with TypeScript: A Complete Guide

When working with Express.js and TypeScript, you may encounter situations where you want to ensure that certain properties exist on the req.body object. Specifically, you might want to declare that specific fields are available in the request body, giving you stronger type checks and reducing potential errors. In this guide, we'll walk through a simple yet effective method to achieve this.

Understanding the Problem

In a typical Express route handler, you might define a function like this:

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

However, if you want to access properties from req.body, like req.body.xxx, without TypeScript throwing errors, you need to customize the type of the request. By default, the express.Request type does not have awareness of the specific structure of your req.body which can lead to type errors.

The Solution: Extending the Request Type

To address this issue, you can create a custom interface that extends the existing express.Request type. This will allow you to specify the expected structure of the request body, providing strong type checking and better code clarity. Here’s how you can effectively implement this approach:

Step 1: Define the Body Type

Begin by defining an interface for the expected body of the request. For example, in the case of a login request, it might look like this:

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

Step 2: Extend the Express Request Type

Next, create a new interface that extends from express.Request and includes the defined body type:

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

Step 3: Use the Custom Request Type

Finally, update your route handler to utilize this new request type instead of the default express.Request:

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

By implementing these steps, TypeScript will now understand that req.body has the properties you specified, thus eliminating type-related errors when you try to access them.

Conclusion

By extending the express.Request type, you can effectively ensure that your req.body has the structure you expect. This approach not only enhances type safety but also improves the maintainability of your code. So, the next time you're working with Express and TypeScript, remember to utilize this strategy to ensure that your request bodies are properly typed!

With clearer and more manageable code, you can focus on building robust applications without the headache of unexpected runtime errors.