The fifth hardest challenge listed in the “easy” section of Coderbyte.

closestEnemy.js

function closestEnemy(matrix) {
  
  let length = matrix.length
  
  let isValid = matrix.some(v => v.includes(2))
  
  if (!isValid) return -1
  
  let startingPoint
  
  for (let i = 0; i < length; i++) {
    for (let j = 0; j < length; j++) {
      
      if (matrix[i][j] === 1) {
        
        startingPoint = [i, j]
      }
    }
  }
  
  let directions = [[-1,0],[0,1],[1,0],[0,-1]]
  
  let count = 1
  let queue = [startingPoint]

  while (queue.length > 0) {

    let [y, x] = queue.pop()

    for (let dir of directions) {

      let [dy, dx] = dir
      
      let newY = y + dy >= 0 ? y + dy % length : length - 1
      let newX = x + dx >= 0 ? x + dx % length : length - 1
      
      if (matrix[newY][newX] === 2) return count
          
      queue.push([newY, newX])
    }
    
    count++
  }
}