JavaScript The way to improve jQuery code performance [Selector point of view]

I want to understand the best way to improve the performance of jQuery code.

Actually, I know how to cache the jQuery selectors to not touch the DOM multiple times as follow:

The worst way

$('.selector').text('Text');
$('.selector').text('New Text');

The better way

var elem = document.querySelectorAll('.selector');
$(elem).text('Text');
$(elem).text('New Text');

The best way

var $elem = $('.selector');
$elem.text('Text');
$elem.text('New Text');

First Question: Why the third method is faster than the second, and what actually $(elem) do here?

Second Question: When I use .data() in jQuery, I access the internal cache, and don't touch the DOM, so what's the internal cache in JavaScript?

Answer:1

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