ECMAScript modules allow developers to organize code into reusable components. The .mjs file extension tells Node.js to interpret the JavaScript file as an ECMAScript module instead of CommonJS. An MJS file is a source code file written in JavaScript containing an ES Module for Node.js apps. Developers can also use the .js extension for ECMAScript modules outside of Node.js.
Specifiers reference files in import and export statements. There are three types of specifiers: relative specifiers like ‘./startup.js’, bare specifiers like ‘lodash/fp’, and absolute URLs. Using path specifiers scales better when importing many modules compared to bare specifiers.
In summary, .js files are general JavaScript files. CJS and MJS extensions specify the module format – CommonJS and ECMAScript modules. .js files use CommonJS by default in Node.js. To use ECMAScript modules, use the .mjs extension or set “type”:”module” in package.json.
I reordered the sentences to first introduce ECMAScript modules and the .mjs extension, then explain specifiers, and end with a summary comparing file extensions. I aimed to keep sentences between 6-17 words, changed order of sentences and words, removed unnecessary details, and ensured word forms weren’t changed. Let me know if you would like me to modify the text further.
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