Скачать или смотреть Resolving undefined Request Body Issues with Express Router

Learn how to properly use `express.urlencoded` and `express.json` to prevent `req.body` from returning undefined when using Express Router in your Node.js application.
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This video is based on the question https://stackoverflow.com/q/71852075/ asked by the user 'georgevil73' ( https://stackoverflow.com/u/17322491/ ) and on the answer https://stackoverflow.com/a/71852201/ provided by the user 'Ehsan Shavandi' ( https://stackoverflow.com/u/16000277/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Fixing req.body Undefined Issue with Express Router

If you have ever worked with Express.js, you may have encountered the frustrating problem where your req.body returns undefined, especially when using routers. This issue can hinder the functionality of your application and leave you puzzled, wondering what went wrong. In this post, we will explore a common scenario leading to this issue and how to resolve it effectively.

Understanding the Problem

Imagine you are building a simple web application using Node.js and Express where users can submit articles through a form. You've set up your application and routes, but upon form submission, you find that req.body is returning undefined. This can be both confusing and frustrating, as it breaks the flow of your application.

The Code Example

Consider the following relevant sections from the server and routing files, illustrating the issue:

server.js

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

articles.js (routes)

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

In this example, req.body remains undefined when the form in new.ejs is submitted.

The Solution

The key to solving this issue lies in the proper order of your middleware setup in the server file (server.js). Here’s how to ensure that the request body is correctly parsed and accessible:

Step-by-Step Fix

Use Middleware Properly: Ensure that any middleware that processes the request body is applied before your routers.

Add express.json() Middleware: If you are also sending JSON data, include the express.json() middleware.

Here’s the revised setup:

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

Summary of Changes

Place app.use(express.urlencoded({ extended: true })); and app.use(express.json()); before app.use("/articles", articleRouter);.

Ensure that your routers can access the request body by applying necessary middleware first.

Conclusion

In web application development, understanding the order of middleware is crucial for reliable data processing. By ensuring that body-parsing middleware is defined before your route handlers, you can resolve the issue of req.body returning undefined. Next time you face a similar issue, remember to check your middleware setup!

Now that you have the solution, go ahead and apply it to your project. Happy coding!