how to set an id while appending using jquery code example

Example: id to id for append jquery

var e = $('<div style="display:block; float:left;width:'+width+'px; height:'+height+'px; margin-top:'+positionY+'px;margin-left:'+positionX+'px;border:1px dashed #CCCCCC;"></div>');
$('#box').append(e);    
e.attr('id', 'myid');