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JavaScript imports guide (Everything you need to know, in 5 minutes)

Default import

import process from "node:process";

process.env.MY_VAR

• Imports the module’s default export (if one exists).
• Shorthand for import { default as X } from "Y".
• If the default export is an object (for example the process object in Node.js), calling methods via that object (e.g., process.on(...)) uses the correct object as the this context.
• Use this when the module exports a stateful object or one “main” entity.

Named import

import { env } from "node:process";

env.MY_VAR

• Brings only the explicitly exported property as a raw, static reference.
• If you import a function or method via named import and then call it without its owning object, you may lose the original this binding (so this may be undefined).
• Reduces bundle size (although tree-shakers are quite good at this, it will make compilation faster).
• Still runs code in the imported module.
• Usage: pure or stateless functions and constants, reducing import size.