How to detect key pressed in TypeScript?

Question

What would be the semantically equivalent syntax in typescript to the following line in javascript

//Some knockout event handler.
myFunc(data : string, evt : Event) {
    //If enter or tab key up were detected add the excuse to the collection.
    if(evt.enterKey || evt.which == 9)
        //Do Something
}

The trouble I'm having here is unlike regular javascript event, typescript Event class does not have a property enterKey or which. So how do I detect which key is being pressed without getting typescript compile error and the ugly red wiggly underline?

Answer 1

You need register the event, for example:

class EventHandler {
    static RegisterKeyPress(input: string){
        document.getElementById(input).addListener('keypress', (e: KeyboardEvent) =>{
           //You have yout key code here
            console.log(e.keyCode);
        }
    }
}

Happy coding!

Answer 2

For React Users

  private onKeyDown = (e: React.KeyboardEvent<HTMLDivElement>) => {
    console.log(e.key)
  }

where HTMLDivElement is the type of whichever element onKeyDown is attached to.

Answer 3

You need to use the more specialised event type KeyboardEvent, as shown below:

myFunc(data : string, evt : KeyboardEvent)

If you want to also remove errors for evt.enterKey you'll need to add it by extending the interface - although I'm not aware that this is a real property as it isn't technical a control key, like CTRL, SHIFT or ALT, which all have properties on the event:

interface KeyboardEvent {
    enterKey: boolean;
}