Difference between two html time inputs

Question

I try to calculate the difference between two HTML time input elements. At the moment that one of the times is changed, there has to be recalculated, unfortunately I can not do this for each other. Who can help me?

    <input type="time"  id="start" value="10:00" >
<input type="time" id="end" value="12:30" >

<input id="diff">


<script>
var start = document.getElementById("start").value;
var end = document.getElementById("end").value;

document.getElementById("start").onchange = function() {diff(start,end)};
document.getElementById("end").onchange = function() {diff(start,end)};


function diff(start, end) {
    start = start.split(":");
    end = end.split(":");
    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);

    return (hours < 9 ? "0" : "") + hours + ":" + (minutes < 9 ? "0" : "") + minutes;
}

document.getElementById("diff").value = diff(start, end);
</script>

Answer 1

This time difference code is amazing! So if all you need is for it to update itself, I copied and slightly remodeled your code for you. Again, your code is amazing :)

<input type="time"  id="start" value="10:00" >
<input type="time" id="end" value="12:30" >

<input id="diff">


<script>
var start = document.getElementById("start").value;
var end = document.getElementById("end").value;

document.getElementById("start").onchange = function() {diff(start,end)};
document.getElementById("end").onchange = function() {diff(start,end)};


function diff(start, end) {
    start = document.getElementById("start").value; //to update time value in each input bar
    end = document.getElementById("end").value; //to update time value in each input bar
    
    start = start.split(":");
    end = end.split(":");
    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);

    return (hours < 9 ? "0" : "") + hours + ":" + (minutes < 9 ? "0" : "") + minutes;
}

setInterval(function(){document.getElementById("diff").value = diff(start, end);}, 1000); //to update time every second (1000 is 1 sec interval and function encasing original code you had down here is because setInterval only reads functions) You can change how fast the time updates by lowering the time interval
</script>

Is this what you want, if not, tell me, I'll be happy to help with this magnificent code :)