ts-node

What is ts-node?

The ts-node npm package is a TypeScript execution engine and REPL for Node.js. It allows developers to run TypeScript files directly without precompiling them to JavaScript. This is particularly useful for development purposes where you can execute scripts or run a REPL environment without an additional build step.

What are ts-node's main functionalities?

Execute TypeScript files

Run a TypeScript file directly from the command line without prior compilation.

ts-node script.ts

REPL

Start a TypeScript REPL (Read-Eval-Print Loop) to execute TypeScript code interactively.

ts-node

Transpile Only Mode

Run TypeScript files without type checking for faster execution, suitable for development.

ts-node --transpile-only script.ts

Type Checking

Enable type checking when running a TypeScript file, ensuring that the code adheres to the defined types.

ts-node --type-check script.ts

Integration with Testing Frameworks

Use ts-node to run TypeScript tests with Mocha or other Node.js testing frameworks.

mocha --require ts-node/register tests/**/*.spec.ts

Other packages similar to ts-node

esbuild-register

esbuild-register uses the esbuild bundler to transpile TypeScript and JavaScript files on the fly. It is known for its speed and efficiency compared to ts-node, which can be slower due to its full type checking.

babel-node

babel-node is a part of the Babel toolchain that allows running TypeScript and modern JavaScript directly. It is similar to ts-node but uses Babel for transpilation, which can be more configurable and supports a wider range of JavaScript features and experimental syntax.

sucrase-node

sucrase-node is a development tool that allows super-fast development builds. It is similar to ts-node but focuses on speed by avoiding full type checking and supporting a subset of TypeScript features.

swc-node

swc-node is a TypeScript/JavaScript compiler that uses SWC, a super-fast compiler written in Rust. It is designed to be a faster alternative to ts-node, especially for larger codebases.

README

TypeScript Node

TypeScript execution environment and REPL for node. Works with typescript@>=1.5.

Installation

npm install -g ts-node

# Install a TypeScript compiler (requires `typescript` by default).
npm install -g typescript

Features

• Execute TypeScript files with node
• Interactive REPL
• Execute (and print) TypeScript through the CLI
• Uses source maps
• Loads compiler options and .d.ts files from tsconfig.json

Usage

# Execute a script as you would normally with `node`.
ts-node script.ts

# Starts the TypeScript REPL.
ts-node

# Execute code with TypeScript.
ts-node -e 'console.log("Hello, world!")'

# Execute, and print, code with TypeScript.
ts-node -p '"Hello, world!"'

# Pipe scripts to execute with TypeScript.
echo "console.log('Hello, world!')" | ts-node

Mocha

mocha --compilers ts:ts-node/register,tsx:ts-node/register [...args]

Tape

ts-node node_modules/tape/bin/tape [...args]

Gulp

# Just create a `gulpfile.ts` and run `gulp`.
gulp

How It Works

TypeScript Node works by registering the TypeScript compiler for the .ts, .tsx and - when allowJs is enabled - .js extensions. When node.js has a file extension registered (the require.extensions object), it will use the extension internally with module resolution. By default, when an extension is unknown to node.js, it will fallback to handling the file as .js (JavaScript).

P.S. This means that if you don't register an extension, it'll be compiled as JavaScript. When ts-node is used with allowJs, JavaScript files are transpiled using the TypeScript compiler.

Loading tsconfig.json

Typescript Node uses tsconfig.json automatically, use -n to skip loading tsconfig.json.

NOTE: You can use ts-node together with tsconfig-paths to load modules according to the paths section in tsconfig.json.

Configuration Options

You can set options by passing them in before the script.

Note: These are in addition to the node.js CLI arguments.

ts-node --compiler ntypescript --project src --ignoreWarnings 2304 hello-world.ts

• --project, -P Path to load TypeScript configuration from (JSON file, a directory containing tsconfig.json, or false to disable) (also process.env.TS_NODE_PROJECT)
• --compiler, -C Use a custom, require-able TypeScript compiler compatible with typescript@>=1.5.0-alpha (also process.env.TS_NODE_COMPILER)
• --ignore Specify an array of regular expression strings for ts-node to skip compiling as TypeScript (defaults to /node_modules/, false to disable) (also process.env.TS_NODE_IGNORE)
• --ignoreWarnings, -I Set an array of TypeScript diagnostic codes to ignore (also process.env.TS_NODE_IGNORE_WARNINGS)
• --disableWarnings, -D Ignore all TypeScript errors (also process.env.TS_NODE_DISABLE_WARNINGS)
• --compilerOptions, -O Set compiler options using JSON (E.g. --compilerOptions '{"target":"es6"}') (also process.env.TS_NODE_COMPILER_OPTIONS)
• --fast, -F Use TypeScript's transpileModule mode (no type checking, but faster compilation) (also process.env.TS_NODE_FAST)
• --no-cache Skip hitting the compiled JavaScript cache (also process.env.TS_NODE_CACHE)
• --cache-directory Configure the TypeScript cache directory (also process.env.TS_NODE_CACHE_DIRECTORY)

Programmatic Usage

require('ts-node').register({ /* options */ })

// Or using the shortcut file.
require('ts-node/register')

This will register the TypeScript compiler for "on the fly" compilation support of .ts and .tsx files during the run of the script. From here you can use require to bring in modules from TypeScript files:

var someModule = require('path_to_a_typescript_file');

License

MIT