How to code function DATEDIFF JAVASCRIPT

Question

This is a function javascript when i want to know how many days between FROM - TO (DATE)... When i use: ex: dateDiff('2011-03-26','2015-09-28') maybe it's incorrect at return result how many days between from <-> to (DATE) Who can test to help me! Thanks

function dateDiff(from, to) {
  dayofthisYear = {
    0: 365,
    1: 365,
    2: 366,
    3: 365
  }
  febuary = {
    0: 28,
    1: 28,
    2: 29,
    3: 28
  }
  norMonth = {
    1: 31,
    3: 31,
    5: 31,
    7: 31,
    8: 31,
    10: 31,
    12: 31,
    4: 30,
    6: 30,
    9: 30,
    11: 30
  }
  stackFrom = from.split('-', 3);
  stackTo = to.split('-', 3);
  stackFrom[1] /= 1;
  stackTo[1] /= 1; //Assign 08/=1;=>8 for Array True Key
  stackFrom[2] /= 1;
  stackTo[2] /= 1;
  diff = 0;
  if (stackFrom[0] == stackTo[0]) {
    ispecialYear = stackFrom[0] % 4;
    myMonth = norMonth;
    myMonth[2] = febuary[ispecialYear];
    if (stackFrom[1] == stackTo[1]) {
      diff = stackTo[2] - stackFrom[2];
    } else {
      for (var m = stackFrom[1]; m <= stackTo[1]; m++) {
        if (m == stackFrom[1]) {
          diff += myMonth[m] - stackFrom[2];
        } else if (m == stackTo[1]) {
          diff += stackTo[2];
        } else {
          diff += myMonth[m];
        }
      }
    }
  } else {
    for (var y = stackFrom[0]; y <= stackTo[0]; y++) {
      ispecialYear = y % 4;
      if (y == stackFrom[0] | y == stackTo[0]) {
        myMonth = norMonth;
        myMonth[2] = febuary[ispecialYear];
        if (y == stackFrom[0]) {
          for (var m = stackFrom[1]; m <= 12; m++) {
            if (m == stackFrom[1]) {
              diff += myMonth[m] - stackFrom[2];
            } else {
              diff += myMonth[m];
            }
          }

        } else {
          for (var m = stackTo[1]; m >= 1; m--) {
            if (m == stackTo[1]) {
              diff += stackTo[2];
            } else {
              diff += myMonth[m];
            }
          }
        }
      } else {
        diff += dayofthisYear[ispecialYear];
      }
    }
  }
  return diff;
}