JSFiddle - React, Tailwind, and code Playground

HTML

<!doctype html> 
<html> 
<head> 
    <meta charset="utf-8"> 
    <title>Yandex</title> 

</head> 
<body> 
    <a href="((http://yandex.ru))">Яндекс</a>, 
    <a href="((http://yandex.com))">Yandex</a> 
</body> 
<script>

var elems1 = document.getElementsByTagName('a'), // return 2 lements, elems1.length = 2 
    elems2 = document.querySelectorAll("a");  // return 2 elements, elems2.length = 2 

document.body.appendChild(document.createElement("a")); 

console.log(elems1.length, elems2.length);  // now elems1.length = 3! 
                                            // while elems2.length = 2
</script>
</html>