Getting difference between two times

Question

I can't find the solution here in SO so I posted this question. This how I get time difference, but what I am getting is NaN. I've been looking for the cause but with no avail. Any ideas are appreciated.

var totaltime = "";
var check = true;
var timefrom = "1:00";
var timeto = "11:00";
//var timefrom = "10:00";
//var timeto = "19:00";

if (check) {
  //console.log(toSeconds(data[0].timefrom))
  var difference = Math.abs(toSeconds(timefrom) - toSeconds(timeto));
  // format time differnece
  var result = [
    Math.floor(difference / 3600), // an hour has 3600 seconds
    Math.floor((difference % 3600) / 60), // a minute has 60 seconds
    difference % 60
  ];
  // 0 padding and concatation
  console.log(result)
  totaltime = result.map(function(v) {
    return v < 10 ? '0' + v : v;
  }).join(':');
  check = false;
}

console.log(totaltime)

function toSeconds(time_str) {
  //    console.log(time_str)
  // Extract hours, minutes and seconds
  var parts = time_str.split(':');
  // compute  and return total seconds
  return parts[0] * 3600 + // an hour has 3600 seconds
    parts[1] * 60 + // a minute has 60 seconds
    +
    parts[2]; // seconds
}