Typescript - Runtime Methods

runtimeMethods.ts

interface MusicKeyboard {
    playC(): string;
}


function addMusicKeyboardMethods(object: Object): MusicKeyboard {
    Object.defineProperties(object, {
        "playC": function() {
            return "Playing C on Keyboard";
        }
    });
    return <MusicKeyboard>object;
}


let a: Object = {};
let aWrappedAsMusicKeyboard: MusicKeyboard =  addMusicKeyboardMethods(a);
aWrappedAsMusicKeyboard.playC();