function swap(arr,i,j) {
  tmp = arr[i]; arr[i] = arr[j]; arr[j] = tmp;
}
function sortAndGetLargest (arr) {
  tmp = arr[0]; // largest elem
  for (i=0; i<arr.length; i++) {
    if (arr[i] > tmp) tmp = arr[i];
    for (j=i+1; j<arr.length; j++)
      if (arr[i] < arr[j]) swap(arr,i,j);
  }
  return tmp;
}
var largest = sortAndGetLargest([99,2,43,8,0,21,12]);
console.log(largest); // should be 99, but prints 0