TypeScript isJavaScript with syntax for types.

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

ts
constuser= {
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
constuser= {
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 5.8 is now available

What is TypeScript?

JavaScript and More

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

A Result You Can Trust

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

Safety at Scale

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

Adopt TypeScript Gradually

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 howTypeScript can catch mistakes in your editor.

js
functioncompact(arr) {
if (orr.length >10)
returnarr.trim(0,10)
returnarr
}

No editor warnings in JavaScript files

This code crashes at runtime!

JavaScript file

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

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 */
functioncompact(arr) {
if (arr.length >10)
returnarr.trim(0,10)
Property 'trim' does not exist on type 'any[]'.2339Property 'trim' does not exist on type 'any[]'.
returnarr
  }

Using JSDoc to give type information

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

JavaScript with JSDoc

ts
functioncompact(arr:string[]) {
if (arr.length >10)
returnarr.slice(0,10)
returnarr
}

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 seedocumentation and issues in your editor.

ts
interfaceAccount {
id:number
displayName:string
version:1
}
 
functionwelcome(user:Account) {
console.log(user.id)
}
ts
typeResult ="pass" |"fail"
 
functionverify(result:Result) {
if (result ==="pass") {
console.log("Passed")
  }else {
console.log("Failed")
  }
}

TypeScript becomes JavaScript via the delete key.

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

TypeScript file.

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

Types are removed.

js
 
 
functionverify(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

Loved by Developers

Image of the stack overflow logo, and a graph showing TypeScript as the 2nd most popular language

Voted2nd most loved programming language in theStack Overflow 2020 Developer survey

Logo of the State of JS survey

TypeScript wasused by 78% of the2020 State of JS respondents, with93% saying they would use it again.

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