We might not be familiar with the default keys used for impress presentations. In such cases, we can assign our own keys for existing functions and new keys for new functions. Let's see how we can modify the code to add new keys to existing functionalities. Let's add the letter p for previous and n for next.
document.addEventListener("keyup", function ( event ) {
if ( event.keyCode === 9 || ( event.keyCode >= 32 && event.keyCode <= 34 ) || (event.keyCode >= 37 && event.keyCode <= 40) || event.keyCode === 78 || event.keyCode === 80 ) {
switch( event.keyCode ) {
case 80: // letter p
// key codes for default previous keys
api.prev();
break;
case 78: // letter n
// key codes for default next keys
api.next();
break;
}