How to Resolve Cannot Import a Function Issue in Node.js

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The Problem

You’ve defined a function called mobilityRouter in one file and are trying to import it into your main application file, but you're facing an issue where your routes aren't working as expected. Below, I’ll explain how this issue can arise as well as how you can resolve it quickly.

Code Snippet Overview

Here's a brief rundown of your code snippets from both the export and import files:

Exporting the Router Function

In your router logic file, you define the mobilityRouter function as follows:

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

This function takes two parameters and attaches a GET route to the express router.

Importing the Router Function

Then, in your import file, you attempt to use this function:

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

Even though copying the function directly into your import file works, trying to import it gives you the "cannot GET/" error.

The Root Cause of the Problem

The root cause of this issue lies in the handling of the router instance. When you define the mobilityRouter in your export file, you are creating a new router instance which, when invoked, is not connected to the main Express application. Therefore, even though the function runs without errors, the route itself isn’t properly established in the broader context of your app.

The Solution

To fix this issue, you have a couple of options. Here are the two most effective solutions you can implement:

Option 1: Pass the Router as a Parameter

You can modify the mobilityRouter function to accept the router instance as a parameter. This way, you ensure that the same router instance is utilized across your application.

Modify the mobilityRouter function like this:

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

Then in your import file, call it like this:

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

Option 2: Export and Import the Router Instance

Alternatively, you can export the router instance directly from your router logic file and import it into your main file. Here's how to do that:

Modify the Export: Instead of just exporting the mobilityRouter, export the router directly.

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

Import it in your Main File:

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

Conclusion