Question

In a form I have a select box with several options, each representing a report with various variables which influence the rest of the form. Some reports require a start date, others an end date, some require both. I have bound the requirements for each of the reports to the option-elements like this:

<select data-bind="value: ReportId">
    <option value="ID" data-hasStartDate="BOOL" data-hasEndDate="BOOL">Report name</option>
</select>

<input data-bind="visible: hasStartDate" />
<input data-bind="visible: hasEndDate" />

with ID being the id of the report and BOOL being either true or false. I use knockout to data-bind the value of the select-box to the reportId. But I could not figure out how to bind the hasStartDate and hasEndDate-values to a Knockout observable in order to show the appropriate form elements.

Even with custom bindings, I needed a normal jQuery onChange-event in order to apply the values to the Knockout-values hasStartDate and hasEndDate. Is it possible to do it entirely with Knockout itself?

Answer 1

Have you tried using the options binding for select boxes?

You also can’t bind knockout using data-whatever="some value". You always use data-bind, like so: data-bind="bindingtype: value".

Edit:
That being said… If you want to get the data from a selected option in a <select> element, I would use the following jQuery:

$("select").on('change', function() {
   var selectedData = $(this).find(":selected").data("stuff");
});

You can then use selectedData and apply this to a knockout view model.

Working example in a fiddle: http://jsfiddle.net/RZq6Q/4/