TypeScript from Microsoft

Microsoft released a new programming language named TypeScript which is a superset of JavaScript. So unlike CoffeeScript you don't have to learn any new syntax, because TypeScript just extends JavaScript with some features:

• Type annotations
• Classes
• Interface
• Modules
• Pointer function

The project is Open Source (Apache License) and you can compile the code with the TypeScript compiler for Node.js.

Example: Create a class

TypeScript

class Greeter {
    greeting: string;
    constructor (message: string) {
        this.greeting = message;
    }
    greet() {
        return "Hello, " + this.greeting;
    }
}   

JavaScript

var Greeter = (function () {
    function Greeter(message) {
        this.greeting = message;
    }
    Greeter.prototype.greet = function () {
        return "Hello, " + this.greeting;
    };
    return Greeter;
})();

Example: Interface

TypeScript

// Definition
interface Picture {
    src: string;
}

function getUrl(myImg: Picture) {
    return 'http://i.mg/' + myImg.src;
}

JavaScript

You don't need to specify that you implement the interface, it just needs to match the interface’s definition!

var hey_jeah = {src: 'a_leet_img.svg'},
    hey_jeah_url = getUrl(hey_jeah);

Further reading

Official page
http://www.typescriptlang.org

TypeScript: JavaScript Development at Application Scale
http://blogs.msdn.com/b/somasegar/archive/2012/10/01/typescript-javascript-development-at-application-scale.aspx

The obligatory TypeScript reaction post by Mark Rendle
http://blog.markrendle.net/2012/10/02/the-obligatory-typescript-reaction-post/