Question

I have Dijit.form.FilteringSelect which dynamicly loads from web service content of dropdown.

I want to preselect first element. How can I do this?

Answer 1

It depends on your implementation.

If you first load data and then create dojo/store/Memory which feeds dijit/form/FilteringSelect then:

// sync only for dojo/store/Memory
var store = filteringSelect1.store;
filteringSelect1.set("value", store.getIdentity(store.data[0]));

More robust synchronous or asynchronous way would be querying the store:

when(store.query(function(item, index, items) {
    return index == 0;
}), function(results) {
    filteringSelect2.set("value", store.getIdentity(results[0]));
});

See these two example in action at jsFiddle: http://jsfiddle.net/phusick/DaA3a/

If your filteringSelect is backed up by dojo/store/JsonRest then your REST service must support querying by index (in addition to querying by id):

restStore.query({ index: 0 }).then(function(item) {
    filteringSelect1.set("value", restStore.getIdentity(item));  
});

See a bit more complex example (simulating such a REST service via sinon.js fakeServer) at jsFiddle: http://jsfiddle.net/phusick/pGt5n/