Workshop › Connect Four › Step 10 of 38

Where does the disc land?

What we are doing

In this game you choose only a column; the disc falls to the lowest empty hole. dropRow(col) finds it: it looks from the bottom row upwards and stops at the first empty cell. If there is none, it returns -1.

```js
// The lowest empty row in a column, or -1 when the column is full.
function dropRow(col) {
  for (let row = ROWS - 1; row >= 0; row--) {
    if (board[row][col] === 0) return row
  }
  return -1
}
```

What it means

• The loop counts down from the bottom row (5) to the top row (0).
• === asks "is it equal?". At the first empty cell, return row gives that row back and leaves the function.
• If the loop ends without finding one, the column is full: return -1.

Your turn

Under reset, after an empty line, write the comment and dropRow.

Skills: Loops, Functions

← Draw every frame Play a column →

All steps

1. A dark background
2. A drawing function
3. The blue board
4. One hole
5. A whole row
6. All 42 holes
7. The board in memory
8. Discs in their colors
9. Draw every frame
10. Where does the disc land?
11. Play a column
12. Taking turns
13. Click to play
14. The next disc
15. Whose turn?
16. Playing with the keyboard
17. Keys 1 to 7
18. A disc on its way
19. Gravity
20. Watch it fall
21. Inside the board?
22. Walking along a line
23. Four in a row?
24. We have a winner
25. Circle the four
26. Who won?
27. A draw
28. Play again
29. Try a move and take it back
30. Win, or block
31. Don't help the player
32. Prefer the middle
33. The computer's turn
34. Only on your turn
35. You and the computer
36. Counting wins
37. Show the score
38. Build it yourself: the loser starts