TypeScript Announcement: static type safety for JavaScript scale

The Large-Scale Web App Scaling Wall

Building Single Page Applications (SPAs) requires writing thousands of lines of client-side JavaScript. JavaScript's dynamic typing makes maintaining massive codebases difficult—simple typos in property names result in runtime crashes.

Microsoft has announced TypeScript, a typed superset of JavaScript compiled by Anders Hejlsberg (creator of C#).

Key Concepts of TypeScript

TypeScript adds optional static types, class layouts, and modular interfaces to standard JavaScript:

// Early class syntax in TypeScript 0.8
interface User {
    username: string;
    email: string;
}

class DashboardController {
    private activeUser: User;

    constructor(user: User) {
        this.activeUser = user;
    }

    public render(): void {
        console.log("Rendering dashboard for " + this.activeUser.username);
    }
}

Compile-to-JavaScript Output

The TypeScript compiler (tsc) type-checks code and compiles it down to standard ECMAScript 3/5 JavaScript compatible with any browser, bringing compile-time safety and IDE autocomplete to web applications.