In Javascript, how do I tell if a user is pressing two keys at the same time?

Question

In Javascript, how do I tell if a user is pressing two keys at the same time?

For example, I have drawn a circle in the middle of the screen. I want to move it up while

Answer 1

Maybe you can do it by keeping track of keydown and keyup event for each key and you'll know if two keys are being held at the same time.

Sample pseudo-code:

var keydown = {};

function onkeydown(event) {
   keydown[event.key] = true;
}

function onkeyup(event) {
   keydown[event.key] = false;
}

// in some function at some other places

if (keydown['up'] && keydown['right']) {
  move_diagonal('up', 'right');
}
elseif (keydown['up'] && keydown['left']) {
  move_diagonal('up', 'left');
}
elseif .. blah blah