The “Error [err_require_esm]: require() of ES Module” is a common stumbling block for many developers, especially those transitioning from CommonJS modules to ES modules in Node.js. As Node.js has evolved, support for ES modules has become standard, but errors can occur when trying to mix the two module types. If you’ve seen this error, you’re likely trying to use the require() function to import an ES module, which is not supported by default in Node.js for ES modules.

This issue typically arises when working with modern JavaScript libraries that now use ES modules, such as importing import syntax in a require() context. Thankfully, fixing this error is not as complex as it seems. By understanding the cause and applying a few strategies, you can get your code running smoothly. In this article, we’ll break down the “Error [err_require_esm]: require() of ES Module”, show you how to solve it, and offer some tips to avoid it in the future.

How to Fix “Error [err_require_esm]: require() of ES Module

The “Error [err_require_esm]: require() of ES Module” can be frustrating, but fortunately, it’s not too difficult to resolve once you understand what causes it. This error occurs when you try to use the require() function, which is part of the CommonJS module system, to import an ES Module. These two systems—CommonJS and ES Modules—are incompatible in many ways, which is why you encounter this issue in Node.js.

To fix this error, you need to first identify whether the module you are trying to load is written using ES Module syntax. If the module uses import and export statements, it is an ES Module and cannot be loaded using the require() function. There are several solutions to fix this error, depending on your specific situation.

One of the most straightforward methods is to switch from using require() to using import. If you’re working with a modern Node.js environment that supports ES Modules natively, you can modify your project to use import statements instead of require(). This involves changing the way you import modules across your entire codebase, but it’s a long-term solution that aligns with the future direction of JavaScript development.

Another simple solution is to enable ES Module support in Node.js. By default, Node.js uses CommonJS, but you can enable ES Modules by adding “type”: “module” in your package.json file. This tells Node.js to treat all .js files in your project as ES Modules. Alternatively, you can rename your JavaScript files from .js to .mjs, which is another way to signal to Node.js that the files should be treated as ES Modules.

If you don’t want to convert your entire project to ES Modules, a quick workaround is to use dynamic import(). This method allows you to load ES Modules asynchronously, even in a CommonJS project. It doesn’t require you to convert everything to ES Modules but lets you import them when needed. This approach is useful if you only need to load a few ES Modules and don’t want to overhaul your entire codebase.

Lastly, using a transpiler like Babel is another option. Babel can convert ES Module code into CommonJS code, allowing you to continue using require() in your project while still importing ES Modules. However, this introduces a build step, so it’s most useful in projects where you are already using a transpiler.

By identifying the best method for your specific project, you can resolve the “Error [err_require_esm]: require() of ES Module” and ensure your Node.js environment runs smoothly.

Common Mistakes When Fixing “Error [err_require_esm]”

When fixing the “Error [err_require_esm]: require() of ES Module”, developers often make several common mistakes. These mistakes can prevent the error from being properly resolved and may even introduce new issues. Understanding these common pitfalls will help you avoid them and make the troubleshooting process smoother.

• Mixing CommonJS and ES Module Syntax: One of the most frequent mistakes is mixing the require() and import syntax in the same file or project. Node.js treats CommonJS and ES Modules differently, so combining them can lead to unexpected errors. If you are using ES Modules, ensure that all modules in your project are imported using the import statement, and vice versa for CommonJS.
• Not Configuring the Project for ES Modules: Another common issue is forgetting to enable ES Module support in Node.js. By default, Node.js uses CommonJS. To switch to ES Modules, you need to either add “type”: “module” to your package.json or rename your files to have the .mjs extension. Failing to do this will result in Node.js treating .js files as CommonJS, leading to the [err_require_esm] error.
• Using ES Modules Without a Transpiler in Older Node.js Versions: If you are working with an older version of Node.js that doesn’t fully support ES Modules, you may encounter issues when trying to use import or export statements. In these cases, many developers forget to use a transpiler like Babel to convert ES Module syntax into CommonJS, leading to compatibility problems.
• Forgetting to Use Dynamic Import for ES Modules: In cases where you only need to load an ES Module dynamically within a CommonJS project, using the static require() function instead of dynamic import() is a common mistake. The dynamic import() function allows you to load ES Modules asynchronously and can resolve the error without needing to switch the entire project to ES Modules.
• Incorrect File Extensions: Many developers overlook the importance of file extensions when switching to ES Modules. While .js is typically used for CommonJS, .mjs signals to Node.js that the file is an ES Module. Forgetting to rename files accordingly, or using .js without the appropriate “type”: “module” configuration in package.json, can result in Node.js treating the file as CommonJS, triggering the [err_require_esm] error.
• Not Understanding Module Type in Third-Party Libraries: Sometimes the issue arises from third-party libraries that have transitioned to ES Modules, while your project is still using CommonJS. Developers often fail to check whether the library they are importing has switched to ES Modules and attempt to load it using require(), resulting in the error.

By avoiding these common mistakes and understanding the key differences between CommonJS and ES Modules, you can effectively resolve the [err_require_esm] error and ensure smooth operation in your Node.js project.

Summary

The “Error [err_require_esm]: require() of ES Module” is a common issue faced by developers working with Node.js as they transition to using ES modules. By understanding the difference between CommonJS and ES modules, and applying the appropriate solutions such as dynamic imports or renaming your files to .mjs, you can resolve this error and future-proof your project. With Node.js increasingly adopting ES modules as the standard, addressing this issue sooner rather than later will benefit your workflow in the long run.

FAQ

Can I mix require() and import in the same project?

Yes, but it’s not recommended. It’s better to either use CommonJS or fully transition to ES modules to avoid compatibility issues.

Can I fix the error using Babel?

Yes, Babel can transpile your ES modules back into CommonJS code, allowing you to use require() without errors.

Is switching to ES modules mandatory in Node.js?

While it’s not mandatory, it’s becoming the standard, and switching sooner will help ensure your project is future-proof.