Sudoku safe placement row condition in JS

sudoku-row-condition.js

// puzzleArray is the game board being solved. A 9x9 matrix
// emptyCell = {rowIndex: INT , colIndex: INT } INT = coordinates of currently empty cell
// num = integer value 1-9 being tested

const rowSafe = (puzzleArray, emptyCell, num) => {
  // -1 is return value of .find() if value not found
 return puzzleArray[ emptyCell.rowIndex ].indexOf(num) == -1
}