How to get selected menu option from a knockout.js observableArray? - select

Question

I feel like I'm missing something very basic, but I can't get a dropdown menu to work as I expect using Knockout.js.
I have a set of objects I want to present in a menu, and I need to find the selected option and post that to the server. I can get the menu to render, but can't seem to get the value of the selected item. My view model looks like this:
function ProjectFilterItem( name, id ) {
this.Name = name;
this.Id = id;
}
function FilterViewModel() {
this.projectFilters = ko.observableArray([
new ProjectFilterItem( "foo", "1" ),
new ProjectFilterItem( "bar", "2" ),
new ProjectFilterItem( "baz", "3" )
]);
this.selectedProject = ko.observable();
}
ko.applyBindings( new FilterViewModel() );
and my view markup looks like this:
<select
id = "projectMenu"
name = "projectMenu"
data-bind = "
options: projectFilters,
optionsText: 'Name', /* I have to enquote the value or I get a JS error */
optionsValue: 'Id', /* If I put 'selectedProject here, nothing is echoed in the span below */
optionsCaption: '-- Select Project --'
"
></select>
<b>Selected Project:</b> <span data-bind="text: selectedProject"></span>
How do get the selected menu item to display in the span, and to post to the server? (I assume the observable I render in the span is the same one I'd post.) Do I need another property in the ProjectFilterItem, like this.selected = ko.observable(false); ? If so, how would I declare it as the target of the value?

Answer 1

You just need use with the value binding to bind the selected value:
From the options documentation:
Note: For a multi-select list, to set which of the options are
selected, or to read which of the options are selected, use the
selectedOptions binding. For a single-select list, you can also read
and write the selected option using the value binding.
In your example:
<select
id = "projectMenu"
name = "projectMenu"
data-bind = "
value: selectedProject,
options: projectFilters,
optionsText: 'Name',
optionsValue: 'Id',
optionsCaption: '-- Select Project --'
"
></select>
See Demo.