Adding Window.event Handler To Typescript

Answer :

This

window.addEventListener('keydown', keyDownListener, false) 

window is defined will all events in lib.d.ts and this particular listener as

 addEventListener(type: "keydown", listener: (ev: KeyboardEvent) => any, useCapture?: boolean): void; 

or this, if you want to keep your original "style",

window.onkeydown = (ev: KeyboardEvent): any => {      //do something }