jiti

What is jiti?

The jiti npm package is a runtime TypeScript and ES Module (ESM) loader that allows you to import TypeScript files, ESM, or JSON modules dynamically in a Node.js environment without the need for prior compilation. It is designed to be a zero-config, drop-in replacement for dynamic imports and require calls, providing just-in-time transpilation of code.

What are jiti's main functionalities?

Dynamic Import of TypeScript Files

This feature allows you to dynamically import TypeScript files at runtime. The jiti function is called with the current filename to create a context, and then it is used to import a TypeScript module, which is transpiled just-in-time.

const jiti = require('jiti')(__filename)
const myModule = jiti('./my-module.ts')

Dynamic Import of ESM

With this feature, jiti can dynamically import ES Module files. The 'esmResolve' option enables proper resolution of ESM modules, allowing them to be loaded at runtime without prior compilation.

const jiti = require('jiti')(__filename, { esmResolve: true })
const myESMModule = jiti('./my-esm-module.mjs')

Dynamic Import of JSON Modules

This feature enables the dynamic import of JSON modules. By using jiti, you can load JSON files at runtime, which can be useful for configuration files or other data that needs to be imported into your application.

const jiti = require('jiti')(__filename)
const config = jiti('./config.json')

Other packages similar to jiti

esbuild-register

esbuild-register is a package that uses the esbuild bundler to transpile TypeScript and modern JavaScript on the fly for Node.js. It is similar to jiti in that it allows just-in-time transpilation, but it leverages the fast esbuild compiler.

ts-node

ts-node is a TypeScript execution engine and REPL for Node.js. It provides on-the-fly transpilation of TypeScript into JavaScript, allowing developers to execute TypeScript directly without pre-compilation. ts-node is widely used and has more configuration options compared to jiti.

babel-register

babel-register is a Babel hook that transpiles files on the fly when they are required. It is similar to jiti in providing just-in-time transpilation, but it uses Babel, which has a wide range of plugins and is highly configurable.

README

jiti

This is the active development branch. Check out jiti/v1 for legacy v1 docs and code.

🌟 Used in

Docusaurus, ESLint, FormKit, Histoire, Knip, Nitro, Nuxt, PostCSS loader, Rsbuild, Size Limit, Slidev, Tailwindcss, Tokenami, UnoCSS, WXT, Winglang, Graphql code generator, Lingui, Scaffdog, Storybook, ...UnJS ecosystem, ...60M+ npm monthly downloads, ...6M+ public repositories.

✅ Features

• Seamless TypeScript and ESM syntax support for Node.js
• Seamless interoperability between ESM and CommonJS
• Asynchronous API to replace import()
• Synchronous API to replace require() (deprecated)
• Super slim and zero dependency
• Custom resolve aliases
• Smart syntax detection to avoid extra transforms
• Node.js native require.cache integration
• Filesystem transpile with hard disk caches
• ESM Loader support
• JSX support (opt-in)

[!IMPORTANT] To enhance compatibility, jiti >=2.1 enabled interopdefault using a new Proxy method. If you migrated to 2.0.0 earlier, this might have caused behavior changes. In case of any issues during the upgrade, please report so we can investigate to solve them. 🙏🏼

💡 Usage

CLI

You can use jiti CLI to quickly run any script with TypeScript and native ESM support!

npx jiti ./index.ts

Programmatic

Initialize a jiti instance:

// ESM
import { createJiti } from "jiti";
const jiti = createJiti(import.meta.url);

// CommonJS (deprecated)
const { createJiti } = require("jiti");
const jiti = createJiti(__filename);

Import (async) and resolve with ESM compatibility:

// jiti.import(id) is similar to import(id)
const mod = await jiti.import("./path/to/file.ts");

// jiti.esmResolve(id) is similar to import.meta.resolve(id)
const resolvedPath = jiti.esmResolve("./src");

If you need the default export of module, you can use jiti.import(id, { default: true }) as shortcut to mod?.default ?? mod.

// shortcut to mod?.default ?? mod
const modDefault = await jiti.import("./path/to/file.ts", { default: true });

CommonJS (sync & deprecated):

// jiti() is similar to require(id)
const mod = jiti("./path/to/file.ts");

// jiti.resolve() is similar to require.resolve(id)
const resolvedPath = jiti.resolve("./src");

You can also pass options as the second argument:

const jiti = createJiti(import.meta.url, { debug: true });

Register global ESM loader

You can globally register jiti using global hooks. (Important: Requires Node.js > 20)

import "jiti/register";

Or:

node --import jiti/register index.ts

🎈 jiti/native

You can alias jiti to jiti/native to directly depend on runtime's import.meta.resolve and dynamic import() support. This allows easing up the ecosystem transition to runtime native support by giving the same API of jiti.

⚙️ Options

debug

• Type: Boolean
• Default: false
• Environment variable: JITI_DEBUG

Enable verbose logging. You can use JITI_DEBUG=1 <your command> to enable it.

fsCache

• Type: Boolean | String
• Default: true
• Environment variable: JITI_FS_CACHE

Filesystem source cache (enabled by default)

By default (when is true), jiti uses node_modules/.cache/jiti (if exists) or {TMP_DIR}/jiti.

Note: It is recommended that this option be enabled for better performance.

moduleCache

• Type: String
• Default: true
• Environment variable: JITI_MODULE_CACHE

Runtime module cache (enabled by default).

Disabling allows editing code and importing the same module multiple times.

When enabled, jiti integrates with Node.js native CommonJS cache-store.

transform

• Type: Function
• Default: Babel (lazy loaded)

Transform function. See src/babel for more details

sourceMaps

• Type: Boolean
• Default false
• Environment variable: JITI_SOURCE_MAPS

Add inline source map to transformed source for better debugging.

interopDefault

• Type: Boolean
• Default: true
• Environment variable: JITI_INTEROP_DEFAULT

Jiti combines module exports with the default export using an internal Proxy to improve compatibility with mixed CJS/ESM usage. You can check the current implementation here.

alias

• Type: Object
• Default: -
• Environment variable: JITI_ALIAS

You can also pass an object to the environment variable for inline config. Example: JITI_ALIAS='{"~/*": "./src/*"}' jiti ....

Custom alias map used to resolve IDs.

nativeModules

• Type: Array
• Default: ['typescript']
• Environment variable: JITI_NATIVE_MODULES

List of modules (within node_modules) to always use native require() for them.

transformModules

• Type: Array
• Default: []
• Environment variable: JITI_TRANSFORM_MODULES

List of modules (within node_modules) to transform them regardless of syntax.

importMeta

Parent module's import.meta context to use for ESM resolution. (only used for jiti/native import).

tryNative

• Type: Boolean
• Default: Enabled if bun is detected
• Environment variable: JITI_TRY_NATIVE

Try to use native require and import without jiti transformations first.

jsx

• Type: Boolean | {options}
• Default: false
• Environment Variable: JITI_JSX

Enable JSX support using @babel/plugin-transform-react-jsx.

See test/fixtures/jsx for framework integration examples.

Development

• Clone this repository
• Enable Corepack using corepack enable
• Install dependencies using pnpm install
• Run pnpm dev
• Run pnpm jiti ./test/path/to/file.ts

License

Published under the MIT license. Made by @pi0 and community 💛