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Discover how to fix the `Unexpected token 'export'` error that occurs when deploying Node.js apps on Heroku, caused by mixing module syntax.
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Resolving the Unexpected token 'export' Error on Heroku for Node.js Applications

If you're a developer working with Node.js, you might have encountered an error message like this when deploying your web application to Heroku:

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

This issue typically arises when there's a mix-up between CommonJS and ES6 module syntax. In this guide, we'll walk you through understanding this error, why it happens, and how to resolve it effectively.

Understanding the Problem

You may find that your Node.js application runs perfectly on your local environment. However, upon deployment to Heroku, you receive a syntax error related to the use of the export statement. The following error message is indicative of this issue:

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

This error occurs when you're trying to use ES6 module exports in a CommonJS environment, which Heroku defaults to when it runs Node.js applications.

What Are CommonJS and ES6 Modules?

CommonJS (CJS): This is the module standard used in Node.js. You use require() to import modules and module.exports to export them.

ES6 Modules: This is the modern JavaScript module system. You use import to bring in modules and export to make them available for use in other files.

Why Do You Encounter This Error?

The error arises because you're mixing these two syntaxes in your code. For example, while you're using require() to import modules, you also have the export function statement in your module, leading to confusion in the loader.

Here's a snippet that exemplifies the issue:

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

How to Fix the Error

To resolve the Unexpected token 'export' error, you need to use a consistent module syntax throughout your code. Given that your Node.js version is using CommonJS, you'll want to switch your exports to CJS syntax. Here's how to do it:

Step 1: Change export to module.exports

Replace the export statement with module.exports. Your corrected code should look like this:

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

Step 2: Deploy to Heroku

Once you make this change, commit your updates and redeploy to Heroku. The syntax error should no longer appear, and your application should run smoothly.

Conclusion

Mixing CommonJS and ES6 module syntax can lead to frustrating errors, particularly when moving from a local development environment to a cloud platform like Heroku. By ensuring that you consistently use require and module.exports, your application should function correctly upon deployment.

If you still experience issues, double-check your entire codebase for mixed syntax and ensure that your Node.js and npm versions in the engines field align with your project requirements.

By following these steps, you can effectively eliminate the Unexpected token 'export' error. Happy coding!