Question

From:
andrew whittakers example showing result numbers in a custom jquery autocomplete implementation

 _response: function(contents){
        $.ui.autocomplete.prototype._response.apply(this, arguments);
        $(this.element).trigger("autocompletesearchcomplete", [contents]);
    }

why [contents] and not contents ?

Answer 1

It’s a requirement from jQuery‘s trigger function that the second parameter be an array (prior to 1.6.2), thus the wrapping to make it an array. From the trigger docs (emphasize by me):

$('#foo').bind('custom', function(event, param1, param2) {
  alert(param1 + "\n" + param2);
});
$('#foo').trigger('custom', ['Custom', 'Event']);

The event object is always passed as the first parameter to an event
handler, but if additional parameters are specified during a
.trigger() call, these parameters will be passed along to the handler
as well. To pass more than one parameter, use an array as shown here.
As of jQuery 1.6.2, a single parameter can be passed without using an
array.

So as of 1.6.2, it’s actually not necessary to wrap the single argument in an array.