syntax for 'using' in javascript

I'm watc$$anonymous$$ng 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 t$$anonymous$$s in C#:

using Pathfinding;

how would t$$anonymous$$s line be written in javascript?