Workshop › Battleship › Step 28 of 35

H for heat

What we are doing

The H key turns the heat map on and off.

```js
document.addEventListener('keydown', (event) => {
  if (event.key === 'h' || event.key === 'H') showHeat = !showHeat
  else return
  event.preventDefault()
})
```

What it means

• 'h' || 'H' accepts both, with or without Caps Lock.
• !showHeat flips it.
• Other keys return right away; only keys the game uses reach preventDefault, so the page keeps its normal keys.

Your turn

Under the pointerdown listener, write the keydown listener.

Skills: Keyboard and mouse input

← See the heat map Show their ships at the end →

All steps

1. A 10 by 10 sea
2. A function for any sea
3. Your own sea
4. Draw again and again
5. Grids and ships as lists
6. A random fleet
7. Two fleets
8. Which ship is here?
9. Fire at a square
10. Show the shots
11. Your shot
12. Tap to fire
13. A message line
14. Hit or miss?
15. See your own fleet
16. Sinking ships
17. Darker hits on a sunk ship
18. Outline sunk ships
19. Win in as few shots as you can
20. A record of their shots
21. Take turns
22. The computer shoots back
23. You can lose too
24. A heat map
25. Shoot the hottest square
26. Hunt around a hit
27. See the heat map
28. H for heat
29. Show their ships at the end
30. A keyboard cursor
31. Move with the arrows
32. Fire with Enter, play again
33. Your best game
34. A side panel
35. Build it yourself: ships apart