How can I convert time to decimal number in JavaScript?

Question

I'm too lazy to fill out my time sheet at work by the end at the end of every month, so I've started adding some functions to our PDF form. Acrobat Pro offers to make advanced calculations using JavaScript, but I'm stuck with this problem.

I have two fields in which I enter the time when I start/end working. I want to calculate my overtime and output the result in a third field. however, I want the output to be decimal, so when I make half an hour overtime, the result would be 0.5

Example: my work time is 8.5 hours, I start a 7.30 and finish at 16.00 (4 pm).

My code so far:

var workTime = this.getField ("Work time").value;
var startTime = this.getField ("Start time").value;
var endTime = this.getField ("End time").value;

event.value = workTime - (endTime - startTime);

Answer 1

Separate hours and minutes, divide minutes by 60, add to hours.

function timeStringToFloat(time) {
  var hoursMinutes = time.split(/[.:]/);
  var hours = parseInt(hoursMinutes[0], 10);
  var minutes = hoursMinutes[1] ? parseInt(hoursMinutes[1], 10) : 0;
  return hours + minutes / 60;
}

Answer 2

In my case I use it for calculating time on invoice.

The input could contain these 6 ways to write it for the user :

• 1 -> 1 hour 0 minutes
• 1,2 -> 1 hour 12 minutes
• 1.5 -> 1 hour 30 minutes
• 1:30 -> 1 hour 30 minutes
• 1h40 -> 1 hour 40 minutes
• 45m -> 0 hour 45 minutes

So I used this (thanks to Amadan), here is working code :

function time2dec(tIn) {
    if(tIn == '') 
        return 0;
    if(tIn.indexOf('h') >= 0 || tIn.indexOf(':') >= 0)
        return hm2dec(tIn.split(/[h:]/));
    if(tIn.indexOf('m') >= 0)
        return hm2dec([0,tIn.replace('m','')]);
    if(tIn.indexOf(',') >= 0)
        return parseFloat(tIn.split(',').join('.')).toFixed(2);
    if(tIn.indexOf('.') >= 0)
        return parseFloat(tIn);
    return parseInt(tIn, 10);
}

function hm2dec(hoursMinutes) {
    var hours = parseInt(hoursMinutes[0], 10);
    var minutes = hoursMinutes[1] ? parseInt(hoursMinutes[1], 10) : 0;
    return (hours + minutes / 60).toFixed(2);
}

Example of use (with jQuery) :

var qty = time2dec($('#qty').val());
var price = parseFloat($('#price').val());
var total = (qty * price).toFixed(2);

Hope it could help some of us.

Answer 3

Another way ;)

var aHours = 4.45;

var aHoursInMinutes = (Math.floor(aHours) * 60 )+ ((aHours - Math.floor(aHours)) * 100);
 // 285 minutes;

var afromMinutesToHours = 
(Math.floor(aHoursInMinutes /60) + ((aHoursInMinutes - (60* Math.floor(aHoursInMinutes /60)))/100));
 // 4.45 hours;

var bHours = 0.33;

var bHoursInMinutes = (Math.floor(bHours) * 60 )+ ((bHours - Math.floor(bHours)) * 100); // 33 minutes;

var bFromMinutesToHours = 
(Math.floor(bHoursInMinutes / 60) + (( bHoursInMinutes - (60 * Math.floor(bHoursInMinutes / 60)))/100)); // 0.33 hours;

var resultInMinutes = aHoursInMinutes + bHoursInMinutes;
var resultToHours = 
(Math.floor(resultInMinutes / 60) + (( resultInMinutes - (60 * Math.floor(resultInMinutes  / 60)))/100)); // 5.18 hours;

Answer 4

As alternative, I was curious if this could be done using Date.parse, and it can.

The following code returns the same values as the selected answer, except for garbage input in which case it returns zero. The 1970 date is used because that is UNIX time zero.

Note that MDN says, "It is not recommended to use Date.parse as until ES5, parsing of strings was entirely implementation dependent."

var test = [undefined, null, "", "garbage", "0", "00:00", "  01:11", "3:44", "2:3", "5.06"];
var hours = 0;
var html = "<table>";

for (var i = 0; i < test.length; i++) {
  html += "<tr>";
  html += "<td>" + test[i] + "</td>";
  hours = timeStringToFloat(test[i]);
  html += "<td>" + hours + "</td>";
  hours = timeStringToNumber(test[i]);
  html += "<td>" + hours + "</td>";
  html += "<td>" + hoursToString(hours) + "</td>";
  html += "</tr>";
}
stdout.innerHTML = html;

function timeStringToNumber(time) {
  return ((new Date(("01 Jan 1970 " + time || "").replace(".", ":") + " GMT")) / 3600000) || 0;
}

function timeStringToFloat(time) {
  try {
    var hoursMinutes = time.split(/[.:]/);
    var hours = parseInt(hoursMinutes[0], 10);
    var minutes = hoursMinutes[1] ? parseInt(hoursMinutes[1], 10) : 0;
    return hours + minutes / 60;
  } catch (e) {
    return "ERROR";
  }
}

function hoursToString(hours) {
  var minutes = hours * 60;
  return (
    ("00" + Math.floor(minutes / 60)).slice(-2) +
    ":" +
    ("00" + Math.round(minutes % 60)).slice(-2)
  );
}

body {
  font-family: sans-serif;
  font-size: 12px;
}

h4 {
  color: white;
  background-color: steelblue;
  padding: 0.5em;
}

table {
  border-collapse: collapse;
}

table td {
  border: 1px solid gray;
  min-height: 1em;
}

<h4>Test Output:</h4>
Method A is the original and Method B the alternative.
<table>
  <thead>
    <tr>
      <th>String</th>
      <th>Method A</th>
      <th>Method B</th>
      <th>ToString</th>
    </tr>
  </thead>
  <tbody id="stdout"></tbody>
</table>

*

function timeStringToNumber( time ) 
{
    return ((new Date(("01 Jan 1970 " + time || "").replace(".",":") + " GMT")) / 3600000) || 0;
}