Default import

import process from "node:process";
// Equivalent to
import { default as process } from "node:process"

process.env.MY_VAR

• Brings in the default export of a module.
• Returns the live object (including this context), so process.on etc. work correctly.
• Usage: modules with a default export defined that require state.

Named import

import { env } from "node:process";

env.MY_VAR

• Brings only the explicitly exported property as a raw, static reference (this = undefined).
• Reduces bundle size (although tree-shakers are quite good at this, it will make compilation faster).
• Usage: pure or stateless functions and constants.

Namespace import

import * as process from "node:process";

process.env.MY_VAR
process.on(...) // Fails

• Collects all exports into a single frozen module namespace object (properties are immutable).
• Methods relying on this break (e.g. process.on), since they’re just functions detached from the real object.
• Usage: static values/functions, not for stateful objects like process.

Side-effect import