<div id="div-01">Here is div-01</div>
<div id="div-02">Here is div-02</div>
Aren't they the same thing ?
Both returning the immediately followed node. I read a lot of articles but seems to me like the same thing, but can't figure where to use one versus other ?
nextElementSibling always returns an element. nextSibling can return any kind of node. They are the same for your example, but different in other cases, e.g.:
<p><span id="span-01">Here is span-01</span>
Some text at the top level
<span id="span-02">Here is span-02</span></p>
In this case, document.getElementById('span-01').nextElementSibling is span-02, but document.getElementById('span-01').nextSibling is the text node containing "Some text at the top level" (or, as pointed out by @Manngo in the comments, the whitespace that separates that text from the element above -- it seems some browsers put whitespace between elements and non-whitespace nodes into separate nodes, while others combine it with the rest of the text).
来源：https://stackoverflow.com/questions/24226571/what-is-the-difference-between-node-nextsibling-and-childnode-nextelementsibling