At 22:24 in the video Dan tries to use his constants as the keys in the object but it doesn't work for him. This is because he did it wrong.

when he did it you ended up with an object that had the strings "UP", "DOWN", etc as the keys but you wanted it to be the numbers that those constants represented. The way that you do that is to put the variables in square brackets. For example.

const UP = 0;
const DOWN = 1;
const LEFT = 2;
const RIGHT = 3;
const object1 = {
 UP: [],
 DOWN: [],
 LEFT: [],
 RIGHT: []
}
 
const object2 = {
 [UP]: [],
 [DOWN]: [],
 [LEFT]: [],
 [RIGHT]: []
}
 
 console.log(object1) => // {UP: Array(0), DOWN: Array(0), LEFT: Array(0), RIGHT: Array(0)}
 console.log(object2) => // {0: Array(0), 1: Array(0), 2: Array(0), 3: Array(0)}
}

and here's an interactive example https://editor.p5js.org/D_Snyder/sketches/r7rHl0QuA

The term for this is Computed Property Names and more details can be found here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Object_initializer#computed_property_names