Workshop › Connect Four › Step 23 of 38

Four in a row?

What we are doing

A new line of four must go through the disc that just landed, so we only look around that disc, in the four directions. wins4(row, col) returns the first line of 4 or more, or null.

```js
const DIRECTIONS = [
  [1, 0],
  [0, 1],
  [1, 1],
  [1, -1],
]

function wins4(row, col) {
  for (const dir of DIRECTIONS) {
    const cells = lineThrough(row, col, dir)
    if (cells.length >= 4) return cells
  }
  return null
}
```

What it means

• DIRECTIONS lists the four directions as [dx, dy] pairs: across, down, and the two diagonals.
• For each direction, if the line through the cell has 4 or more cells, return it.

Your turn

1. Under COLORS write DIRECTIONS.
2. Above function play( write wins4, followed by an empty line.

Skills: Loops, Game states

← Walking along a line We have a winner →

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