jQuery Datepicker onchange event issue

Question

You can use the datepicker's onSelect event.

$(".date").datepicker({
    onSelect: function(dateText) {
        console.log("Selected date: " + dateText + "; input's current value: " + this.value);
    }
});

Live example:

$(".date")
.datepicker({
    onSelect: function(dateText) {
        console.log("Selected date: " + dateText + "; input's current value: " + this.value);
    }
})
.on("change", function() {
    console.log("Got change event from field");
});

<link href="https://code.jquery.com/ui/1.9.2/themes/smoothness/jquery-ui.css" rel="stylesheet" />
<input type='text' class='date'>
<script src="https://code.jquery.com/jquery-1.8.3.min.js"></script>
<script src="https://code.jquery.com/ui/1.9.2/jquery-ui.js"></script>

Unfortunately, onSelect fires whenever a date is selected, even if it hasn't changed. This is a design flaw in the datepicker: It always fires onSelect (even if nothing changed), and doesn't fire any event on the underlying input on change. (If you look in the code of that example, we're listening for changes, but they aren't being raised.) It should probably fire an event on the input when things change (possibly the usual change event, or possibly a datepicker-specific one).

---

If you like, of course, you can make the change event on the input fire:

$(".date").datepicker({
    onSelect: function() {
        $(this).change();
    }
});

That will fire change on the underlying input for any handler hooked up via jQuery. But again, it always fires it. If you want to only fire on a real change, you'll have to save the previous value (possibly via data) and compare.

Live example:

$(".date")
.datepicker({
    onSelect: function(dateText) {
        console.log("Selected date: " + dateText + "; input's current value: " + this.value);
        $(this).change();
    }
})
.on("change", function() {
    console.log("Got change event from field");
});

<link href="https://code.jquery.com/ui/1.9.2/themes/smoothness/jquery-ui.css" rel="stylesheet" />
<input type='text' class='date'>
<script src="https://code.jquery.com/jquery-1.8.3.min.js"></script>
<script src="https://code.jquery.com/ui/1.9.2/jquery-ui.js"></script>

T.J. Crowder's answer (https://stackoverflow.com/a/6471992/481154) is very good and still remains accurate. Triggering the change event within the onSelect function is as close as you're going to get.

However, there is a nice property on the datepicker object (lastVal) that will allow you to conditionally trigger the change event only on actual changes without having to store the value(s) yourself:

$('#dateInput').datepicker({
     onSelect: function(d,i){
          if(d !== i.lastVal){
              $(this).change();
          }
     }
});

Then just handle change events like normal:

$('#dateInput').change(function(){
     //Change code!
});

Your looking for the onSelect event in the datepicker object:

$('.selector').datepicker({
   onSelect: function(dateText, inst) { ... }
});

$('#inputfield').change(function() { 
    dosomething();
});

I wrote this because I needed a solution to trigger an event only if the date changed.

It is a simple solution. Each time the dialog box closes we test to see if the data has changed. If it has, we trigger a custom event and reset the stored value.

$('.datetime').datepicker({
    onClose: function(dateText,datePickerInstance) {
        var oldValue = $(this).data('oldValue') || "";
        if (dateText !== oldValue) {
            $(this).data('oldValue',dateText);
            $(this).trigger('dateupdated');
        }
    }
});

Now we can hook up handlers for that custom event...

$('body').on('dateupdated','.datetime', function(e) {
    // do something
});