Casidoo-180

rotate90

const rotate = v => {
  let n = v.length-1;
  for (let y=0; y < Math.floor(v.length/2); y++) {
    for (let x=0+y; x < v.length-y-1; x++) {
      [v[y][x], v[n-x][y], v[n-y][n-x], v[x][n-y]] = [v[n-x][y], v[n-y][n-x], v[x][n-y], v[y][x]]
    }
  }
  return v;
}

let tests = [ 
  [[[1,2,3],[4,5,6],[7,8,9]], [[7,4,1],[8,5,2],[9,6,3]]],
  [[[1,2,3,4],[4,5,6,7],[7,8,9,10],[11,12,13,14]], [[11,7,4,1],[12,8,5,2],[13,9,6,3],[14,10,7,4]]], 
  [[[1,2,3],[4,5,6],[7,8,9]], [[7,4,1],[8,5,2],[9,6,3]],],
  [[[5]], [[5]],],
  [[[]], [[]]]
]

let isEqual = (v1, v2) => JSON.stringify(v1) === JSON.stringify(v2)

tests.forEach(([input, expected]) => { 
  let observed = rotate(input)
  if (!isEqual(observed, expected)) 
    console.log(`Failure on ${input}: result was ${observed}`);
})

// Output: No failures.