I have the following code, can anyone please tell me what "!!" is here. Thank you.
$('#calendar').fullCalendar({
events: function(start, end, timezone, callback) {
jQuery.ajax({
url: 'schedule.php/load',
type: 'POST',
dataType: 'json',
data: {
start: start.format(),
end: end.format()
},
success: function(doc) {
var events = [];
if(!!doc.result){
$.map( doc.result, function( r ) {
events.push({
id: r.id,
title: r.title,
start: r.date_start,
end: r.date_end
});
});
}
callback(events);
}
});
}
});
I did some Google search, unfortunately I could not find such operator. If you know any web site as reference, please let me know.
Thanks.