syntax for 'using' in javascript

I’m watching a tutorial on some pathfinding resource and the tutorial uses c# but I use java script. I can manage converting what i see in the tut from C# into java script, except for the ‘using’ line. I have no idea what these look like in java script.

the line in question looks like this in C#:

using Pathfinding;

how would this line be written in javascript?

import Pathfinding;