var element = document.querySelector('#textinput');

var throttledInput = Rx.Observable.fromEvent(element, 'keyup').select( function (ev) {
    // Return text value for each key up
    return ev.target.value;
}).throttle(
    // Throttle input by 500ms
    500
).where( function (text) {
    // Only get input more than 2 characters
    return text.length > 2;
}.distinctUntilChanged(
    // Returns only distinct text values
);

// Combine together with an Ajax call
var serviceCall = throttledInput.select( function (text) {
    // Call service wrapped as an Observable sequence
    return queryService(text);
}.switchLatest(
    // Trim out of order requests to ensure we only have the latest
);

// Subscribe to the service call
serviceCall.subscribe( function (results) {
    // Handle the results
}, function (err) {
    // Handle the errors
});