Can someone help with explaining a linkedlist in Javascript

Question

I've read the tutorial loads of time now but I just don't get it. The naming system is confusing. Like

self.head = Node(data, self.head)

wasnt self.head null moments ago? What's happening?

while curr.next:
curr = curr.next

so much reassignment, using the same name over and over without comments makes this stuff so hard to read. What does curr mean? Current? Earlier in the node class they said they have data and a link, but the second parameter is "next". Is this the link? When it printed it it returned an object. This is so confusing

Can anyone help?

(I'm doing it in Javascript as to not "cheat", the tutorial was made in Python and it doesn't feel right making an identical code to the tutorial)

https://code.sololearn.com/Wpj3x4AJ4Nbh/?ref=app