getEmptyBlocks.js

getEmptyBlocks.js

const getEmptyBlocks = (board) => (
  board.reduce((lineData, line, idxColumn) => { // Iterate over columns
    const result = line.reduce((data, row, idx) => { // Iterate over lines
      if (row !== 0) return data; // If value is different of zero, response last iterate
      return [[idxColumn, idx], ...data]; // Join last iterate (or default value) with new data
    }, []); // Default value to reduce in line

    return [...lineData, ...result]; // Join old value with new value and return to next reduce
  }, []) // Default value to reduce in column
);

const board = [
  [2, 2, 2, 2],
  [0, 4, 16, 16],
  [8, 8, 0, 32],
  [0, 0, 0, 64]
];

console.log(getEmptyBlocks(board));
// Response [ [ 1, 0 ], [ 2, 2 ], [ 3, 2 ], [ 3, 1 ], [ 3, 0 ] ]