NodeNext and Bundler Resolution

NodeNext models modern Node.js module loading and usually requires explicit .js extensions in relative ESM imports, even from .ts source files. Bundler resolution supports package exports but commonly accepts extensionless relative imports because a bundler rewrites them. Select a mode based on the actual deployment.

Reading the code: This model prints the two choices; the values describe strategies but do not configure tsc. A real NodeNext project uses matching module/moduleResolution settings and ESM imports such as "./utils.js".

Keep the boundary clear: An extensionless import accepted by bundler resolution may fail in unbundled Node.js ESM at runtime.

Save the code as nodenext-bundler-resolution.ts. The result below was captured after compiling this exact example with strict TypeScript checking and executing the emitted JavaScript in Node.js.

TypeScript code

type Mode = "nodenext" | "bundler";
const config: Record<Mode, string> = {
  nodenext: "Node.js loader rules",
  bundler: "Bundler loader rules"
};
console.log(config.nodenext);
console.log(config.bundler);

Verified output

Node.js loader rules
Bundler loader rules

Build: npx tsc --strict --target es2022 --module commonjs --lib es2022,dom,esnext.disposable nodenext-bundler-resolution.ts; run: node nodenext-bundler-resolution.js. The exact filename may be changed freely. When a multi-file project exists, prefer its tsconfig.json and build scripts.

This model prints the two choices; the values describe strategies but do not configure tsc. A real NodeNext project uses matching module/moduleResolution settings and ESM imports such as "./utils.js".

The output shown above comes from the initialized values in this program. Replacing a type annotation alone does not transform a JavaScript value.

This separate mini-project demonstrates real imports, exports, or declarations across files. Create each file in one folder, then compile and run main.js. The example was checked separately from the single-file program.

util.ts

export const value=17;

main.ts

import {value} from "./util.js";console.log(value);

ESM setup: create package.json containing {"type":"module"}, use npx tsc --strict --target es2022 --module nodenext --moduleResolution nodenext main.ts, and run node main.js. Keep the package.json alongside the emitted JavaScript.

Verified output from the mini-project

17

An extensionless import accepted by bundler resolution may fail in unbundled Node.js ESM at runtime.

Check both the TypeScript diagnostic and the emitted JavaScript behavior. A program can compile correctly and still need runtime validation or error handling.

Try importing "./util" versus "./util.js" in a NodeNext ESM example, and note which import type-checks.

Before running your change, write down the type you expect TypeScript to infer and the output you expect JavaScript to print. Then check both predictions.

NodeNext models modern Node.

Try the practice change and re-run the exact program to test your understanding.