Stefanacef

const arr=[1, 2, 3, 4,5, 4, 3, 2, 1, 3, 4]
function migratoryBirds(arr) {
    let objectArr=arr.reduce((obj, b)=> {
        obj[b] = ++obj[b] || 1;
        return obj;
      }, {});
//      console.log(objectArr)
     const maxVal=Math.max(...Object.values(objectArr))
     const num=Object.keys(objectArr).find(key => objectArr[key] === maxVal)