Understanding and Solving the "Cannot Use Import Outside a Module" Error in Node.js

if you are used to writing Node.js scripts, I'm certain that you have stumbled upon the error "cannot use import outside a module". the first thing you did was checking your Node.js version, it says v18.17.1.

You search google for ES6 support in Node.js, it says that the first Node.js version to support ES6-style import and export is version 13.2.0.

So what can be the problem ? why you can't use import/export with Node.js

To understand why, it's essential to delve into the concepts of modules in JavaScript.

JavaScript Modules

Modules in JavaScript are a way to organize and encapsulate code. They allow developers to break down complex codebases into smaller, more manageable pieces. Each module can export specific functionalities, which other modules can import and use.

JavaScript has many modules systems, we will explain only two:

1. CommonJS: used mainly in Node.js environments. It uses require() for importing and module.exports for exporting functionalities.
2. ES6 Modules: The standard for browser-based JavaScript. It uses the import and export statements.

Node.js and ES6: A Complex Relationship

Node.js initially adopted CommonJS module system in 2009.

On the other hand, ES6 introduced a new syntax for modules, using import and export in 2015.

Despite Node.js’s support for ES6 Modules since v13, it doesn’t automatically recognize the import/export syntax, for compatibility concerns, and for the difference in the loading mechanisms; CommonJS loads modules synchronously while ES6 modules support asynchronous loading.

Solutions

1. File Extensions: Use the .mjs extension for your scripts, Node.js treats .mjs files as ES6 modules.

2. Package.json Configuration: Add "type": "module" in your package.json. This informs Node.js that all .js files in the project should be treated as ES6 modules.

3. Transpilers/Bundlers: Tools like Babel or Webpack can transpile ES6 code to CommonJS, making it compatible with Node.js’s default module system.

Conclusion

The introduction of ES6 modules marked a significant step in JavaScript’s evolution, ES6 modules are designed to be more efficient and capable of static analysis, allowing for tree-shaking (removing unused code) and better optimization by JavaScript engines.