Cheat Sheet

ECMAScript Modules Cheat Sheet

Lucas Holmquist
October 12, 2021
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About

ECMAScript modules (ESM) are the official standard format for packaging JavaScript code for reuse. Modules are defined using a variety of import and export statements. 

ESM are already the standard format for front-end development, and now you can use them on the back end with recent versions of Node.js. Although the old module system (CommonJS) has worked for many years, ESM come with many benefits such as asynchronous loading, top-level await, and improved static analysis.

In this cheat sheet you will learn:

  • How to enable ECMAScript modules
  • How to import and export ECMAScript modules

Excerpt

Because Node.js treats code as CommonJS modules by default, module authors will need to tell Node.js to treat the code as ECMAScript Modules by either using the .mjs file extension (as shown in earlier examples) or by using the type field in the package.json file.

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