Scrimba coding challanges

firstDuplicate

//function to find first duplicate in array
function firstDuplicate(nums) {
    let MyObj = {}
    let myArr = []

    for (i=0; i< nums.length ; i++){
        for (j=i+1; j< nums.length; j++){
            if(nums[i] === nums[j]){
                MyObj[nums[i]] = j;
            }
        }
    }

  if (Object.keys(MyObj).length){
      myArr = Object.values(MyObj)
      const min = Math.min(...myArr)
      return(nums[min])
  }
  else{
      return -1
  }

}