Typing TypeScript

Since companies are moving every single application to web, TypeScript gets more and more interesting. JavaScript is nice, but it wasn’t designed for big web applications. TypeScript is a Javascript language extension with very useful features. It isn’t a JavaScript killer. The code is converted to JavaScript and the browser executes pure JavaScript code. We don’t need a TypeScript interpreter.

TypeScript features:

Here is a small example.

module HardWorker {

    export interface ISayHello {
        sayHello(): void;
    }

    export class Developer implements ISayHello {
        public firstName: string;
        public lastName: string;

        constructor(firstName: string, lastName: string) {
            this.firstName = firstName;
            this.lastName = lastName;
        }

        sayHello() {
        }
    }

    export class JavaDeveloper extends Developer {
        sayHello() {
            alert("Hello Java");
        }
    }

    export class DotNetDeveloper extends Developer {
        sayHello() {
            alert("Hello C#");
        }
    }
}

window.onload = () => {
    
    var javaDev = new HardWorker.JavaDeveloper("Max", "Muster");
    var dotNetDev = new HardWorker.DotNetDeveloper("Darko", "Micic");
    
    javaDev.sayHello();
    dotNetDev.sayHello();
};

The compiler generates following JavaScript code. (This code is executed in the browser.)

var __extends = this.__extends || function (d, b) {
    function __() { this.constructor = d; }
    __.prototype = b.prototype;
    d.prototype = new __();
};
var HardWorker;
(function (HardWorker) {
    var Developer = (function () {
        function Developer(firstName, lastName) {
            this.firstName = firstName;
            this.lastName = lastName;
        }
        Developer.prototype.sayHello = function () {
        };
        return Developer;
    })();
    HardWorker.Developer = Developer;    
    var JavaDeveloper = (function (_super) {
        __extends(JavaDeveloper, _super);
        function JavaDeveloper() {
            _super.apply(this, arguments);

        }
        JavaDeveloper.prototype.sayHello = function () {
            alert("Hello Java");
        };
        return JavaDeveloper;
    })(Developer);
    HardWorker.JavaDeveloper = JavaDeveloper;    
    var DotNetDeveloper = (function (_super) {
        __extends(DotNetDeveloper, _super);
        function DotNetDeveloper() {
            _super.apply(this, arguments);

        }
        DotNetDeveloper.prototype.sayHello = function () {
            alert("Hello C#");
        };
        return DotNetDeveloper;
    })(Developer);
    HardWorker.DotNetDeveloper = DotNetDeveloper;    
})(HardWorker || (HardWorker = {}));
window.onload = function () {
    var javaDev = new HardWorker.JavaDeveloper("Max", "Muster");
    var dotNetDev = new HardWorker.DotNetDeveloper("Darko", "Micic");
    javaDev.sayHello();
    dotNetDev.sayHello();
};
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