Async call to backendless data

This works, but it freezes the page during call:

getAllNewEstate: function(callback) {
function NewEstateData() {};
var items = Backendless.Persistence.of( NewEstateData ).find().data;
callback(items)
},

How can i make async call?
I tried:

getAllNewEstate: function(callback) {
function NewEstateData() {};
Backendless.Persistence.of( NewEstateData ).find( function(e) {
console.log('event', e);
callback(e.data);
});
},

no errors, no console.log, nothing

getAllNewEstate: function(callback) {
    function NewEstateData() {};
    Backendless.Persistence.of( NewEstateData ).find( new Backendless.Async(
        function(e) {
             console.log(e);
             callback(e);
        })
    );
}