Cant find the function that echos the files directory

Hi guys,

I want to include some JS to my theme.
I created a folder called “js” in my twentyfifteen child theme folder.

When I want to call the file I write the whole text. is there a function that does that in a more simple way instead of typing the whole directory myself?

<script type=’text/javascript’ src=’https://54.149.xx.xx/wp-content/themes/twentyfifteen-child/js/scroll.js’></script&gt;