function findMaxNumberOfConsecOnes(dec){
  const countConsecOnes = (acc, x) => [acc[0] < acc[1]
                                       ? acc[1]
                                       : acc[0],
                                       x === "1"
                                       ? acc[1] + 1
                                       : 0 ];

  return [...(dec >>> 0).toString(2)]
      .reduce(countConsecOnes, [0,0]);
}

function findMaxNumberOfConsecOnes(dec){
  const countConsecOnes = (acc, x) => [acc[0] < acc[1] ? acc[1] : acc[0],
                                       x === "1" ? acc[1] + 1 : 0 ];

  return [...(dec >>> 0).toString(2)]
      .reduce(countConsecOnes, [0,0]);

function findMaxNumberOfConsecOnes(dec){
  return [...(dec >>> 0).toString(2)]
    .reduce((acc, x) => {
      const current = x === "1" ? acc[1] + 1 : 0;
      const max = Math.max(acc[0], current);
      return [max, current];
  }, [0,0]);
}

function findMaxNumberOfConsecOnes(dec){
  const binStr = (dec >>> 0).toString(2);
  let max = 0, current = 0;
  for (const s of binStr) {
    current = s === "1" ? current + 1 : 0;
    max = Math.max(max, current);
  }
  return max;
}