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Submitted URL: http://1710215722937.abstractedkirobin.com/e28db810-7e5a-4a2f-99e8-7b14fdd804ab?n=1&t=1710215722937&l_next=ahr0chm6ly93d3cubgf0ywh1z28udg9w...
Effective URL: https://www.typescriptlang.org/
Submission: On March 12 via api from US — Scanned from US

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Text Content

Skip to main content
TypeScript
 * Download
 * Docs
 * Handbook
 * Community
 * Playground
 * Tools

in En





TYPESCRIPT IS JAVASCRIPT WITH SYNTAX FOR TYPES.

TypeScript is a strongly typed programming language that builds on JavaScript,
giving you better tooling at any scale.

Try TypeScript Now
Online or via npm

 * Editor Checks
 * Auto-complete
 * Interfaces
 * JSX

ts
const user = {
  firstName: "Angela",
  lastName: "Davis",
  role: "Professor",
}
 
console.log(user.name)Property 'name' does not exist on type '{ firstName: string; lastName: string; role: string; }'.2339Property 'name' does not exist on type '{ firstName: string; lastName: string; role: string; }'.
 

ts
const user = {
  firstName: "Angela",
  lastName: "Davis",
  role: "Professor",
}
 
console.log(user.name)Property 'name' does not exist on type '{ firstName: string; lastName: string; role: string; }'.2339Property 'name' does not exist on type '{ firstName: string; lastName: string; role: string; }'.
 

TypeScript 5.4 is now available


WHAT IS TYPESCRIPT?


JAVASCRIPT AND MORE

TypeScript adds additional syntax to JavaScript to support a tighter integration
with your editor. Catch errors early in your editor.


A RESULT YOU CAN TRUST

TypeScript code converts to JavaScript, which runs anywhere JavaScript runs: In
a browser, on Node.js or Deno and in your apps.


SAFETY AT SCALE

TypeScript understands JavaScript and uses type inference to give you great
tooling without additional code.


GET STARTED

Handbook
Learn the language

Playground
Try in your browser

Download
Install TypeScript



ADOPT TYPESCRIPT GRADUALLY

JavaScript file

Apply types to your JavaScript project incrementally, each step improves editor
support and improves your codebase.

Let's take this incorrect JavaScript code, and see how TypeScript can catch
mistakes in your editor.

js
function compact(arr) {
    if (orr.length > 10)
        return arr.trim(0, 10)
    return arr
}

No editor warnings in JavaScript files

This code crashes at runtime!

JavaScript file


js
// @ts-check
 
function compact(arr) {
  if (orr.length > 10)Cannot find name 'orr'.2304Cannot find name 'orr'.
    return arr.trim(0, 10)
  return arr
}

Adding this to a JS file shows errors in your editor

the param is arr, not orr!

JavaScript with TS Check


js
// @ts-check
 
/** @param {any[]} arr */
function compact(arr) {
    if (arr.length > 10)
      return arr.trim(0, 10)Property 'trim' does not exist on type 'any[]'.2339Property 'trim' does not exist on type 'any[]'.
    return arr
  }

Using JSDoc to give type information

Now TS has found a bad call. Arrays have slice, not trim.

JavaScript with JSDoc


ts
function compact(arr: string[]) {
  if (arr.length > 10)
    return arr.slice(0, 10)
  return arr
}

TypeScript adds natural syntax for providing types

TypeScript file





DESCRIBE YOUR DATA

Describe the shape of objects and functions in your code.

Making it possible to see documentation and issues in your editor.

ts
interface Account {
  id: number
  displayName: string
  version: 1
}
 
function welcome(user: Account) {
  console.log(user.id)
}

ts
type Result = "pass" | "fail"
 
function verify(result: Result) {
  if (result === "pass") {
    console.log("Passed")
  } else {
    console.log("Failed")
  }
}


TYPESCRIPT BECOMES JAVASCRIPT VIA THE DELETE KEY.

ts
type Result = "pass" | "fail"
 
function verify(result: Result) {
  if (result === "pass") {
    console.log("Passed")
  } else {
    console.log("Failed")
  }
}
 

TypeScript file.

ts
type Result = "pass" | "fail"
 
function verify(result: Result) {
  if (result === "pass") {
    console.log("Passed")
  } else {
    console.log("Failed")
  }
}
 

Types are removed.

js
 
 
function verify(result) {
  if (result === "pass") {
    console.log("Passed")
  } else {
    console.log("Failed")
  }
}
 

JavaScript file.


TYPESCRIPT TESTIMONIALS




First, we were surprised by the number of small bugs we found when converting
our code.

Second, we underestimated how powerful the editor integration is.

TypeScript was such a boon to our stability and sanity that we started using it
for all new code within days of starting the conversion.



Felix Rieseberg at Slack covered the transition of their desktop app from
JavaScript to TypeScript in their blog

Read



OPEN SOURCE WITH TYPESCRIPT

Angular

Vue

Jest

Redux

Ionic

Probot

Deno

Vercel

Yarn

GitHub
Desktop


LOVED BY DEVELOPERS

Voted 2nd most loved programming language in the Stack Overflow 2020 Developer
survey



TypeScript was used by 78% of the 2020 State of JS respondents, with 93% saying
they would use it again.

TypeScript was given the award for “Most Adopted Technology” based on
year-on-year growth.


GET STARTED

Handbook
Learn the language

Playground
Try in your browser

Download
Install TypeScript


Made with ♥ in Redmond, Boston, SF & Dublin

© 2012-2024 Microsoft
Privacy


USING TYPESCRIPT

 * Get Started
 * Download
 * Community
 * Playground
 * TSConfig Ref
 * Why TypeScript
 * Design
 * Code Samples
   JavaScriptTypeScript
   
   See how TypeScript improves day to day working with JavaScript with minimal
   additional syntax.
   
   JAVASCRIPT ESSENTIALS
   
    1. Hello World
       
    2. Objects and Arrays
       
    3. Functions
       
    4. Code Flow
       
   
   FUNCTIONS WITH JAVASCRIPT
   
    1. Generic Functions
       
    2. Typing Functions
       
    3. Function Chaining
       
   
   WORKING WITH CLASSES
   
    1. Classes 101
       
    2. This
       
    3. Generic Classes
       
    4. Mixins
       
   
   MODERN JAVASCRIPT
   
    1. Async Await
       
    2. Immutability
       
    3. Import Export
       
    4. JSDoc Support
       
   
   EXTERNAL APIS
   
    1. TypeScript with Web
       
    2. TypeScript with React
       
    3. TypeScript with Deno
       
    4. TypeScript with Node
       
    5. TypeScript with WebGL
       
   
   HELPING WITH JAVASCRIPT
   
    1. Quick Fixes
       
    2. Errors
       
   
   Explore how TypeScript extends JavaScript to add more safety and tooling.
   
   PRIMITIVES
   
    1. Any
       
    2. Literals
       
    3. Union and Intersection Types
       
    4. Unknown and Never
       
   
   TYPE PRIMITIVES
   
    1. Tuples
       
    2. Built-in Utility Types
       
    3. Nullable Types
       
   
   META-TYPES
   
    1. Conditional Types
       
    2. Discriminate Types
       
    3. Indexed Types
       
    4. Mapped Types
       
   
   LANGUAGE
   
    1. Soundness
       
    2. Structural Typing
       
    3. Type Guards
       
    4. Type Widening and Narrowing
       
   
   LANGUAGE EXTENSIONS
   
    1. Enums
       
    2. Nominal Typing
       
    3. Types vs Interfaces
       
   
   


COMMUNITY

 * Get Help
 * Blog
 * GitHub Repo
 * Community Chat
 * @TypeScript
 * Mastodon
 * Stack Overflow
 * Web Repo

MSG