Calculate Time Difference with JavaScript

Question

I have two HTML input boxes, that need to calculate the time difference in JavaScript onBlur (since I need it in real time) and insert the result to new input box.

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Answer 1

This solution works for calculating diff between to separate military times

Example format: start = 23:00 / end = 02:30

function diff(start, end) {
start = start.split(":");
end = end.split(":");
if(Number(start[0]) > Number(end[0]) ) {
  var num = Number(start[0])
  var countTo = Number(end[0]);
  var count = 0;
  for (var i = 1; num != countTo;) {
    num = num + i
    if(num > 24) {
      num = 0
    }
    count++
  }
  var hours = count - 1;
  var startDate = new Date(0, 0, 0, start[0], start[1], 0);
  var endDate = new Date(0, 0, 0, end[0], end[1], 0);
  if(startDate.getMinutes() > endDate.getMinutes()) {
    var hours = count - 2;
    var diff = 60 - (startDate.getMinutes() - endDate.getMinutes());      
  } else {
    var diff = endDate.getMinutes() - startDate.getMinutes();      
  }
  var minutes = diff
} else {
  var startDate = new Date(0, 0, 0, start[0], start[1], 0);
  var endDate = new Date(0, 0, 0, end[0], end[1], 0);
  var diff = endDate.getTime() - startDate.getTime();
  var hours = Math.floor(diff / 1000 / 60 / 60);
  diff -= hours * 1000 * 60 * 60;
  var minutes = Math.floor(diff / 1000 / 60);
}

var returnValue = (hours < 9 ? "0" : "") + hours + ":" + (minutes < 9 ? "0" : "") + minutes

return returnValue;

}