Workshop › Pac-Man-style Maze Chase › Step 4 of 42

A set of pellets

What we are doing

The pellets get eaten, so they must be state, not map. Each pellet is named by a key like '8,15', and all keys go in a Set: a collection where each value is in at most once, with quick has, add and delete.

```js
let pellets // keys of the tiles that still have a pellet
let powers // keys of the tiles that still have a power pellet

const key = (col, row) => col + ',' + row

function fillPellets() {
  pellets = new Set()
  powers = new Set()
  MAZE.forEach((line, row) => {
    ;[...line].forEach((ch, col) => {
      if (ch === '.') pellets.add(key(col, row))
      if (ch === 'o') powers.add(key(col, row))
    })
  })
}

function reset() {
  fillPellets()
}

reset()
```

What it means

key(8, 15) gives '8,15': one string per tile.
new Set() is an empty set; add puts a key in.
fillPellets walks the map like draw does and collects every . and o.
reset() will set up a whole new game; for now it fills the pellets. It runs once before the loop starts.

Your turn

Under COLS, leave an empty line and write the two variables, key, fillPellets and reset.
Above the last line, requestAnimationFrame(loop), write reset().

Skills: Arrays and objects, Game states

← Draw the walls Draw the pellets →

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