Workshop › Sudoku › Step 10 of 28

Move with the arrows

What we are doing

The arrow keys move the selection, wrapping around the edges.

```js
document.addEventListener('keydown', (event) => {
  const moves = { ArrowUp: [-1, 0], ArrowDown: [1, 0], ArrowLeft: [0, -1], ArrowRight: [0, 1] }
  if (moves[event.key]) {
    event.preventDefault()
    const [dr, dc] = moves[event.key]
    selected = { r: (selected.r + dr + 9) % 9, c: (selected.c + dc + 9) % 9 }
  }
})
```

What it means

• moves is a table from key name to a row and column change.
• preventDefault stops the arrows from scrolling the page.
• (selected.r + dr + 9) % 9 wraps: from row 0 going up gives row 8.

Your turn

Above the pointerdown listener, write the keydown listener.

Skills: Keyboard and mouse input

← Click to select Write digits →

All steps

1. Nine by nine
2. Lines and boxes
3. A puzzle from a string
4. The puzzle's own digits
5. Keep drawing
6. The selected cell
7. Light up row, column and box
8. The same digit everywhere
9. Click to select
10. Move with the arrows
11. Write digits
12. The three rules in one loop
13. Show mistakes
14. Solved!
15. A clock
16. The solved message
17. Play again
18. The easiest cell
19. The solver
20. Random order
21. Invent a puzzle
22. A new puzzle every game
23. Hints
24. Best time
25. N for a new puzzle
26. A number pad
27. Tap the pad
28. Build it yourself: undo