How to Wrap the Elements in jQuery Array into jQuery Objects

  java, question

Now the elements taken out of the array can only be used after $ () is wrapped into jQuery object. The code is as follows:
$($(‘#idStr’)[0]).addClass(‘classStr’);
I want to take jQuery objects directly from the array, such as:
$(‘#idStr’).someMethod(0).addClass(‘classStr’);
Is there any way?
Thank you very much

.eq(index)

Or ..

.slice(start, end)