Nodejs plans to support importexport ES6 ECMAScript 2015 modules

The Node.js ecosystem is buzzing with excitement over the increasingly native support for ES6 modules, commonly known as ECMAScript modules or just ESM. This shift promises a more streamlined, modern development experience, aligning Node.js more closely with browser-based JavaScript and paving the way for cleaner, more maintainable code. For developers, understanding these changes and their implications is crucial for staying ahead of the curve and leveraging the full potential of this powerful runtime environment. This enhanced interoperability offers a significant advantage for developers working across both front-end and back-end JavaScript environments.

Understanding ES Modules

ES modules offer a standardized way to encapsulate and share JavaScript code. Unlike the traditional CommonJS module system, which relies on require() and module.exports, ES modules utilize import and export statements. This syntax is more aligned with how modules are handled in browsers and other JavaScript environments, fostering better code reusability and interoperability. This structured approach allows for more explicit control over what parts of a module are exposed and how they are accessed by other parts of the application.

Prior to native support, using ES modules in Node.js required workarounds like transpilation or the use of the .mjs file extension. The move towards integrated support simplifies development workflows and reduces the need for these extra steps. This streamlining is a boon for developers, allowing them to focus on writing code rather than managing module systems.

For instance, imagine a module exporting a utility function:

// utility.mjs export function formatDate(date) { // ... formatting logic ... } 

Another module can then import and use this function:

// main.mjs import { formatDate } from './utility.mjs'; const formatted = formatDate(new Date()); 

Benefits of Native ESM Support

Native ESM support eliminates the need for tools like Babel to transpile ES modules into CommonJS, resulting in faster startup times and improved performance. Developers can write modern, standardized JavaScript without the overhead of conversion processes. This performance boost is particularly noticeable in larger applications with complex dependency trees.

Moreover, native ESM promotes better code organization and maintainability through its explicit import and export system. This clarity reduces the likelihood of unexpected side effects and makes debugging significantly easier. By clearly defining dependencies, ES modules encourage modular design, leading to more robust and scalable applications.

• Faster startup times
• Improved code organization

Transitioning to ESM

While the transition to ESM is largely seamless, developers should be aware of a few key considerations. Existing projects using CommonJS modules can often be migrated incrementally, allowing teams to adopt ESM gradually. This gradual approach minimizes disruption and enables developers to familiarize themselves with the new system while maintaining existing functionality.

It’s also important to be mindful of package compatibility. Ensure that any third-party libraries you rely on are compatible with ESM or have ESM-compatible versions available. The Node.js community is actively working on updating packages to support ESM, but checking compatibility is a crucial step in the migration process.

Here’s a simplified guide to transitioning:

1. Update package.json: Add "type": "module"
2. Change file extensions: Rename .js files to .mjs (or vice-versa depending on your setup)
3. Update import/export statements

Future of Modules in Node.js

The adoption of ES modules marks a significant step forward for Node.js, aligning it with modern JavaScript standards and paving the way for future innovations. The improved interoperability between server-side and client-side JavaScript development simplifies workflows and opens up new possibilities for code sharing and reuse. This convergence is a significant trend in web development, making Node.js an even more attractive platform for building modern applications.

Furthermore, the improved performance and maintainability offered by ESM contribute to the overall health and longevity of the Node.js ecosystem. As the language continues to evolve, developers can expect further enhancements and optimizations related to module management. This commitment to ongoing improvement ensures that Node.js remains a cutting-edge runtime environment.

For those looking to delve deeper into the topic, the official Node.js documentation provides comprehensive information on ESM support.

Learn more about ES modules in Node.js.See our blog post on getting started with modular JavaScript for more practical tips.

FAQ

Q: What is the difference between CommonJS and ES modules?

A: CommonJS uses require() and module.exports, while ES modules use import and export. ES modules are statically analyzable, which allows for optimizations like tree shaking.

Q: How do I handle dynamic imports with ESM?

A: You can use the import() function for dynamic imports, which returns a promise that resolves to the imported module.

[Infographic Placeholder: Illustrating the difference between CommonJS and ESM]

The transition to native ES modules in Node.js is a significant advancement for the JavaScript ecosystem. By understanding the benefits and the steps involved in migrating, developers can leverage this powerful feature to write cleaner, more efficient, and more maintainable code. This shift represents a crucial step in the maturation of Node.js and its continued alignment with modern JavaScript best practices. Start exploring ES modules in your Node.js projects today to experience the advantages firsthand. Explore more related topics like JavaScript modularity, Node.js performance optimization, and modern web development best practices. Dive deeper into these areas to maximize the impact of these new features and stay at the forefront of JavaScript development.

Question & Answer :
I’ve been looking all over the Internet without a clear answer for this.

Currently Node.js uses only CommonJS syntax to load modules, and if you really want to use the standard ECMAScript 2015 modules syntax, you either have to transpile it beforehand or use an external module loader at runtime.

Currently I’m not too positive to use either of those two methods, are the Node.js maintainers even planning to support ECMAScript 2015 modules or not? I haven’t found an hint at all about this.

At the moment Node.js 6.x claims to support 96% of the ECMAScript 2015 features, but there isn’t any reference to modules (Node.js ECMAScript 2015 support link).

Do you know if Node.js will support these modules out of the box, in the near future?

Node.js 13.2.0 & Above

Node.js 13.2.0 now supports ES Modules without a flag 🎉. However, the implementation is still marked as experimental so use in production with caution.

To enable ECMAScript module (ESM) support in 13.2.0, add the following to your package.json:

{ "type": "module" } 

All .js, .mjs (or files without an extension) will be treated as ESM.

There are a number of different options other than entire package.json opt-in, all of which are detailed in the documentation for 13.2.0.

Node.js 13.1.0 & Below

Those still using older versions of Node may want to try the [esm][3] module loader, which is a production-ready implementation of the ES Modules Specificaiton for Node.js:

node -r esm main.js 

Detailed Updates…

23 April 2019

A PR recently landed to change the way ECMAScript modules are detected: https://github.com/nodejs/node/pull/26745

It’s still behind the --experimental-modules flag, but there are major changes in the way modules can be loaded:

• package.type which can be either module or commonjs
  • type: "commonjs":
    • .js is parsed as CommonJS
    • the default for an entry point without an extension is CommonJS
  • type: "module":
    • .js is parsed as an ECMAScript module
    • does not support loading JSON or a native module by default
    • the default for an entry point without an extension is ECMAScript module
• --type=[mode] to let you set the type on entry point. Will override package.type for entry point.
• A new file extension .cjs.
  • this is specifically to support importing CommonJS in the module mode.
  • this is only in the ECMAScript module loader, the CommonJS loader remains untouched, but the extension will work in the old loader if you use the full file path.
• --es-module-specifier-resolution=[type]
  • options are explicit (default) and node
  • by default our loader will not allow for optional extensions in the import, the path for a module must include the extension if there is one
  • by default our loader will not allow for importing directories that have an index file
  • developers can use --es-module-specifier-resolution=node to enable the CommonJS specifier resolution algorithm
  • This is not a “feature”, but rather an implementation for experimentation. It is expected to change before the flag is removed
• --experimental-json-loader
  • the only way to import JSON when "type": "module"
  • when enable all import 'thing.json' will go through the experimental loader independent of mode
  • based on whatwg/html#4315
• You can use package.main to set an entry point for a module
  • the file extensions used in main will be resolved based on the type of the module

17 January 2019

Node.js 11.6.0 still lists ES Modules as experimental, behind a flag.

13 September 2017

Node.js 8.5.0 has been released with support for mjs files behind a flag:

node --experimental-modules index.mjs 

The plan for this is to remove the flag for the v10.0 LTS release.

–Outdated Information. Kept here for historical purposes–

8 September 2017

The Node.js master branch has been updated with initial support for ESM modules: https://github.com/nodejs/node/commit/c8a389e19f172edbada83f59944cad7cc802d9d5

This should be available in the latest nightly (this can be installed via nvm to run alongside your existing install): https://nodejs.org/download/nightly/

And enabled behind the --experimental-modules flag:

package.json

{ "name": "testing-mjs", "version": "1.0.0", "description": "", "main": "index.mjs" <-- Set this to be an mjs file } 

Then run:

node --experimental-modules . 

February 2017:

An Update on ES6 Modules in Node.js

The Node.js guys have decided that the least bad solution is to use the .mjs file extension. The takeaway from this is:

In other words, given two files foo.js and bar.mjs , using import * from 'foo' will treat foo.js as CommonJS while import * from 'bar' will treat bar.mjs as an ES6 Module

And as for timelines…

At the current point in time, there are still a number of specification and implementation issues that need to happen on the ES6 and Virtual Machine side of things before Node.js can even begin working up a supportable implementation of ES6 modules. Work is in progress but it is going to take some time — We’re currently looking at around a year at least.

October 2016:

One of the developers on Node.js recently attended a TC-39 meeting and wrote up a superb article on the blockers to implementing for Node.js:

Node.js, TC-39, and Modules

The basic take-away from that is:

• ECMAScript modules are statically analyzed, and CommonJS are evaluated
• CommonJS modules allow for monkey-patching exports, and ECMAScript modules currently do not
• It’s difficult to detect what is an ECMAScript module and what is CommonJS without some form of user input, but they are trying.
• *.mjs seems the most likely solution, unless they can accurately detect an ECMAScript module without user-input

– Original Answer –

This has been a hot potato for quite some time. The bottom line is that yes, Node.js will eventually support the ES2015 syntax for importing/exporting modules - most likely when the specification for loading modules is finalized and agreed upon.

Here is a good overview of what’s holding Node.js up. Essentially, they need to make sure that the new specification works for Node.js which is primarily conditional, synchronous loading and also HTML which is primarily asynchronous.

Nobody knows for sure right now, but I imagine Node.js will support import/export for static loading, in addition to the new System.import for dynamic loading - while still keeping require for legacy code.

Here’s a few proposals on how Node might achieve this:

• In defense of .js
• .mjs modules