javascript - How to understand the $()? -

in following code, empty jquery selector $() mean? mean $(document)?

 var menu = {   setting:{       issimpledata:true,       treenodekey:"mid",       treenodeparentkey:"pid",       showline:true,       root:{           isroot:true,           nodes:[]       }   } ,   loadmenutree:function(){       $("#menutree").ztree(menu.setting, privilegedate);   } };  $().ready(function(){     menu.loadmenutree(); }); 

does mean $(document)?

no, means empty jquery collection, $.fn.ready doesn’t care what’s in jquery collection:

> $().length 0  > $.fn.ready function (a){return n.ready.promise().done(a),this} 

note how doesn’t make use of this except return chaining. use $(document).ready, $().ready, $('body').ready, $('blink').ready… non-deprecated way passing listener jquery function itself:

$(function () {     menu.loadmenutree(); });