video.js

const video = () => document.querySelector("video")

const codes = {
  space: 32,
  j: 74,
  k: 75,
  l: 76,
}

document.addEventListener("keydown", e => {
  if ( e.keyCode == codes.k ) {
    toggle()
  }
  if (e.keyCode == codes.l) forward()
  if (e.keyCode == codes.j) backword()
})

function forward() {
  video().currentTime = video().currentTime + 10
}

function backword() {
  video().currentTime = video().currentTime - 10
}

function toggle() {
  video().paused ? video().play() : video().pause()
}