typescript

What is typescript?

The TypeScript npm package is a superset of JavaScript that compiles to clean JavaScript output. It adds optional static typing to JavaScript, which can help with the development of large-scale applications and lead to more robust code. TypeScript is designed for the development of large applications and transcompiles to JavaScript.

What are typescript's main functionalities?

Static Type Checking

TypeScript allows you to define types for your variables and function parameters, which helps catch errors at compile time rather than at runtime.

let isDone: boolean = false;

Classes and Interfaces

TypeScript supports modern JavaScript features like classes and interfaces, allowing for more structured and maintainable code.

class Animal {
  name: string;
  constructor(theName: string) { this.name = theName; }
  move(distanceInMeters: number = 0) {
    console.log(`${this.name} moved ${distanceInMeters}m.`);
  }
}

Modules

TypeScript provides support for modules, enabling you to organize your code into separate files and manage dependencies more effectively.

import { ZipCodeValidator } from './ZipCodeValidator';
let myValidator = new ZipCodeValidator();

Generics

Generics enable you to create reusable components that work with a variety of types rather than a single one.

function identity<T>(arg: T): T {
  return arg;
}

Advanced Types

TypeScript offers advanced types like intersection types, union types, and mapped types, which provide powerful ways to work with your data structures.

type Tree<T> = {
  value: T;
  left: Tree<T>;
  right: Tree<T>;
};

Tooling Support

TypeScript integrates with many editors and provides features like autocompletion, type checking, and source navigation, enhancing the development experience.

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Other packages similar to typescript

flow-bin

Flow is a static type checker for JavaScript. It provides similar functionality to TypeScript, offering static typing in JavaScript, but it uses a different syntax and type system.

babel-preset-typescript

Babel preset for TypeScript allows Babel to parse and transpile TypeScript code. While Babel itself is mainly a JavaScript compiler, this preset brings TypeScript support to Babel's ecosystem.

coffeescript

CoffeeScript is a language that compiles into JavaScript. It provides syntactic sugar inspired by Ruby, Python, and Haskell to enhance JavaScript readability and brevity. It does not offer static typing but focuses on cleaner syntax.

elm

Elm is a functional language that compiles to JavaScript. It emphasizes simplicity and quality tooling, and while it is not a direct alternative to TypeScript's type system, it offers strong typing and eliminates runtime exceptions.

dart

Dart is an object-oriented, class-defined, garbage-collected language using a C-style syntax that transcompiles optionally into JavaScript. It includes static typing and is developed by Google, often used for building web and mobile applications.

README

TypeScript

TypeScript is a language for application-scale JavaScript. TypeScript adds optional types to JavaScript that support tools for large-scale JavaScript applications for any browser, for any host, on any OS. TypeScript compiles to readable, standards-based JavaScript. Try it out at the playground, and stay up to date via our blog and Twitter account.

Find others who are using TypeScript at our community page.

Installing

For the latest stable version:

npm install -g typescript

For our nightly builds:

npm install -g typescript@next

Contribute

There are many ways to contribute to TypeScript.

• Submit bugs and help us verify fixes as they are checked in.
• Review the source code changes.
• Engage with other TypeScript users and developers on StackOverflow.
• Help each other in the TypeScript Community Discord.
• Join the #typescript discussion on Twitter.
• Contribute bug fixes.
• Read the language specification (docx, pdf, md).

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact [e-mail] with any additional questions or comments.

Documentation

• TypeScript in 5 minutes
• Programming handbook
• Language specification
• Homepage

Building

In order to build the TypeScript compiler, ensure that you have Git and Node.js installed.

Clone a copy of the repo:

git clone https://github.com/microsoft/TypeScript.git

Change to the TypeScript directory:

cd TypeScript

Install Gulp tools and dev dependencies:

npm install -g gulp
npm install

Use one of the following to build and test:

gulp local             # Build the compiler into built/local.
gulp clean             # Delete the built compiler.
gulp LKG               # Replace the last known good with the built one.
                       # Bootstrapping step to be executed when the built compiler reaches a stable state.
gulp tests             # Build the test infrastructure using the built compiler.
gulp runtests          # Run tests using the built compiler and test infrastructure.
                       # Some low-value tests are skipped when not on a CI machine - you can use the
                       # --skipPercent=0 command to override this behavior and run all tests locally.
                       # You can override the specific suite runner used or specify a test for this command.
                       # Use --tests=<testPath> for a specific test and/or --runner=<runnerName> for a specific suite.
                       # Valid runners include conformance, compiler, fourslash, project, user, and docker
                       # The user and docker runners are extended test suite runners - the user runner
                       # works on disk in the tests/cases/user directory, while the docker runner works in containers.
                       # You'll need to have the docker executable in your system path for the docker runner to work.
gulp runtests-parallel # Like runtests, but split across multiple threads. Uses a number of threads equal to the system
                       # core count by default. Use --workers=<number> to adjust this.
gulp baseline-accept   # This replaces the baseline test results with the results obtained from gulp runtests.
gulp lint              # Runs eslint on the TypeScript source.
gulp help              # List the above commands.

Usage

node built/local/tsc.js hello.ts

Roadmap

For details on our planned features and future direction please refer to our roadmap.