ESM named exports and imports in Node.js

ESM (ECMAScript Modules) are self-contained files that can be imported and exported. They make sharing code between modules easy and create reusable components. To enable ESM support, we can add the following line to the package.json file:

Once ESM support is enabled, ESM modules can be used in Node.js for different functionalities.

ESM named imports and exports are a feature of ESM (ECMAScript Modules) that are used to export and import specific variables and functions from a module in Node.js. For a named export, the export keyword is used, followed by the name of the variable or function that needs to be exported. For a named import, the import keyword is used followed by the name of the variable or function that needs to be imported, surrounded by curly braces.

Once ESM support is enabled, named imports and exports can be used in the program. Here are some examples of different applications of ESM named imports and exports:

Exporting a named variable

To export a named variable, we use the export keyword followed by the name of the variable we want to export. For example:

In module.js, it exports and sets the myVariable variable.

In export-variable.js:

• Line 1: It imports myVariable from module.js.

• Line 3: It prints myVariable on the console.

Exporting a named function

To export a named function, we use the export keyword followed by the name of the function we want to export. For example:

In module.js, it exports and defines the myFunction() function.

In export-function.js:

• Line 1: It imports myFunction from module.js.

• Line 3: It prints myFunction on console.

Exporting a named class

To export a named class, we use the export keyword followed by the name of the class we want to export. For example:

In module.js:

• Line 1: It exports and defines the myClass class.

• Lines 2–4: The constructor prints the statement “MyClass instance created.”

• Lines 6–7: The function myMethod() returns the statement “Hello from myClass!”

In export-class.js:

• Line 1: It imports myClass from module.js.

• Line 3: It initializes a class object myClassInstance using the new keyword.

• Line 4: It prints myClassInstance.myMethod() on console.

Giving named imports different names

The named imports can be given different names when we import them by using the as keyword. For example:

In module.js:

• Line 1: It exports and sets the myVariable variable.

• Lines 2–3: It exports and defines the myFunction() function.

In export-class.js:

• Line 1: It imports myVariable as myNewVariable and myFunction as myNewFunction from module.js.

• Line 3: It prints myNewVariable() on console.

• Line 4: It prints myNewFunction() on console.

ESM modules have many advantages over the CommonJS (CJS) module formatDefault module format in Node.js such as, clarity, namespace management, and tree shakingProcess of removing unused code from a bundle.