You're thinking too much in pure Javascript. Get rid of your listeners on those React lifecycle methods and use event.key
instead of event.keyCode
(because this is not a JS event object, it is a React SyntheticEvent). Your entire component could be as simple as this (assuming you haven't bound your methods in a constructor).
onKeyPressed(e) {
console.log(e.key);
}
render() {
let player = this.props.boards.dungeons[this.props.boards.currentBoard].player;
return (
<div
className="player"
style={{ position: "absolute" }}
onKeyDown={this.onKeyPressed}
>
<div className="light-circle">
<div className="image-wrapper">
<img src={IMG_URL+player.img} />
</div>
</div>
</div>
)
}