HTML / CSS缩进可选，JS缩进必须吗？

So when I get HTML and CSS validated, it's not required to be indented to pass validation. However, when I get JS validated, it needs to be indented to pass. I don't indent any of my code because practically all my pages are relatively short and simple so I actually find it more effort and a waste of space to indent. However, is it especially important that I do so for JS? Is there a reason it's required for JS but not HTML or CSS?So when I get HTML and CSS validated, it's not