Revitalizing my dead JavaScript by building data structures. Here's an incomplete LinkedList that'll be updated over time.

LinkedList.js

class Node {
    constructor(data = 0, next=null) {
        this.data = data;
        this.next = next
    }
}

class LinkedList {
    constructor(value = 0){
        this.head = new Node(value)
    }

    prepend(value) {
        let current = this.head
        let new_node = new Node(value)
        new_node.next = current
        this.head = new_node
        return current
    }

    getValues() {
        let current = this.head
        let result = []
        while (current != null) {
            result.push(current.data)
            current = current.next
        }
        return result
    }

    append(value) {
        let head = this.head
        let new_node = new Node(value)
        if (head == null) {
            head = new_node
            return head
        }

        while(head && head.next != null) {
            head = head.next
        }
        head.next = new_node
        return head
    }

    length() {
        let count = 0
        let head = this.head
        while (head != null) {
            count += 1
            head = head.next
        }
        return count
    }

    reverse() {
        let current = this.head
        // 1 - 2 - 3 - 4
        let prev = null
        let next = null
        while (current != null) {
            next = current.next // 2
            current.next = prev // 1 -> null
            prev = current
            current = next
        }
        // return prev
        this.head = prev
        return this.head
    }
}

const example = new LinkedList(10)
example.prepend(14)
example.append(19)
example.append(15)
example.reverse()
console.log(example.getValues())

I think the Add* methods are incorrect. I'll reimplement them but lmao, JavaScript isn't sweet with DS abeg.
Binary tree (Incomplete):

class BinaryTreeNode {
    constructor(data, left = null, right = null) {
        this.data = data
        this.left = left
        this.right = right
    }
}

class BinaryTree {
    constructor(value){
        this.root = new BinaryTreeNode(value)
    }    

    AddLeftLeaf(leaf, value) {
        leaf.root.left = new BinaryTreeNode(value)
    }

    AddRightLeaf(leaf, value) {
        leaf.root.right = new BinaryTreeNode(value)
    }
}

let example = new BinaryTree(0)
example.AddLeftLeaf(example, 1)
example.AddRightLeaf(example, 2)
example.AddLeftLeaf(example, 3)
example.AddRightLeaf(example, 4)
console.log(example, '\n')