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

Runtime Typescript and ESM support for Node.js.

[!IMPORTANT] This is the support branch for jiti v1. Check out jiti/main for the latest version and unjs/jiti#174 for the roadmap.

Features

• Seamless typescript and ESM syntax support
• Seamless interoperability between ESM and CommonJS
• Synchronous API to replace require
• Super slim and zero dependency
• Smart syntax detection to avoid extra transforms
• CommonJS cache integration
• Filesystem transpile hard cache
• V8 compile cache
• Custom resolve alias

Usage

Programmatic

const jiti = require("jiti")(__filename);

jiti("./path/to/file.ts");

You can also pass options as second argument:

const jiti = require("jiti")(__filename, { debug: true });

CLI

jiti index.ts
# or npx jiti index.ts

Register require hook

node -r jiti/register index.ts

Alternatively, you can register jiti as a require hook programmatically:

const jiti = require("jiti")();
const unregister = jiti.register();

Options

debug

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

Enable debug to see which files are transpiled

cache

• Type: Boolean | String
• Default: true
• Environment Variable: JITI_CACHE

Use transpile cache

If set to true will use node_modules/.cache/jiti (if exists) or {TMP_DIR}/node-jiti

esmResolve

• Type: Boolean | String
• Default: false
• Environment Variable: JITI_ESM_RESOLVE

Using esm resolution algorithm to support import condition.

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: false

Return the .default export of a module at the top-level.

alias

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

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.

experimentalBun

• Type: Boolean
• Default: Enabled if process.versions.bun exists (Bun runtime)
• Environment Variable: JITI_EXPERIMENTAL_BUN

Enable experimental native Bun support for transformations.

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

MIT. Made with 💖