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import { hello } from "./hello";
hello();
When we run index.ts, it prints “Hello world!”.
terminalbun index.ts Hello world!In this case, we are importing from ./hello, a relative path with no extension. Extensioned imports are optional but supported. To resolve this import, Bun will check for the following files in order: ./hello.tsx ./hello.jsx ./hello.ts ./hello.mjs ./hello.js ./hello.cjs ./hello.json ./hello/index.tsx ./hello/index.jsx ./hello/index.ts ./hello/index.mjs ./hello/index.js ./hello/index.cjs ./hello/index.json Import paths can optionally include extensions. If an extension is present, Bun will only check for a file with that exact extension. index.ts
import { hello } from "./hello";
import { hello } from "./hello.ts"; // this works
If you import from "*.js{x}", Bun will additionally check for a matching *.ts{x} file, to be compatible with TypeScript’s ES module support.
index.tsimport { hello } from "./hello";
import { hello } from "./hello.ts"; // this works
import { hello } from "./hello.js"; // this also works
Bun supports both ES modules (import/export syntax) and CommonJS modules (require()/module.exports). The following CommonJS version would also work in Bun.
index.jshello.jsconst { hello } = require("./hello");
hello();
That said, using CommonJS is discouraged in new projects.
Module systems
Bun has native support for CommonJS and ES modules. ES Modules are the recommended module format for new projects, but CommonJS modules are still widely used in the Node.js ecosystem.
In Bun’s JavaScript runtime, require can be used by both ES Modules and CommonJS modules. If the target module is an ES Module, require returns the module namespace object (equivalent to import * as). If the target module is a CommonJS module, require returns the module.exports object (as in Node.js).
Module Typerequire()import * asES ModuleModule NamespaceModule NamespaceCommonJSmodule.exportsdefault is module.exports, keys of module.exports are named exports
Using require()
You can require() any file or package, even .ts or .mjs files.
index.tsconst { foo } = require("./foo"); // extensions are optional
const { bar } = require("./bar.mjs");
const { baz } = require("./baz.tsx");
What is a CommonJS module?
In 2016, ECMAScript added support for ES Modules. ES Modules are the standard for JavaScript modules. However, millions of npm packages still use CommonJS modules.CommonJS modules are modules that use module.exports to export values. Typically, require is used to import CommonJS modules.my-commonjs.cjsconst stuff = require("./stuff");
module.exports = { stuff };
The biggest difference between CommonJS and ES Modules is that CommonJS modules are synchronous, while ES Modules are asynchronous. There are other differences too.
ES Modules support top-level await and CommonJS modules don’t.
ES Modules are always in strict mode, while CommonJS modules are not.
Browsers do not have native support for CommonJS modules, but they do have native support for ES Modules via Module Resolution - Bun,AI智能索引,全网链接索引,智能导航,网页索引
- How Bun resolves modules and handles imports in JavaScript and TypeScript