Theremove function of the AVL tree appears to delete the entire tree by setting the root property of the tree toundefined if the root value is removed.

This is because the function's callthis.root = balanceUpstream( node.parent ); has parameternode.parent = null ifnode is the root (see commented out function call below). FunctionbalanceUpstream will then immediately returnundefined whichremove assigns tothis.root deleting the tree.

I have fixed this in my implementation of avl-tree.js using a ternary operator:

remove( value ) {        const node = super.find( value );        if ( node ) {            const found = super.remove( value );            const parent = node.parent ? node.parent : this.root;            this.root = balanceUpstream( parent );            //this.root = balanceUpstream( node.parent );            return found;        }        return false;    }

Posted as a (potential) issue as I am not sure whether this is an issue only in my implementation which differs somewhat from the one in this repository.

Cheers!