Linked list implementation using Javscript

• append(value) adds a new node containing value to the end of the list or to start if list is empty
• prepend(value) adds a new node containing value to the start of the list
• size() returns the total number of nodes in the list
• head() returns the first node in the list
• tail() returns the last node in the list
• at(index) returns the node at the given index or error message if there is no node in the requested index
• pop() removes the last element from the list
• contains(value) returns true if the passed in value is in the list and otherwise returns false
• find(value) returns the index of the node containing value, or null if not found
• toString() returns your LinkedList objects as strings in the following format: ( value ) -> ( value ) -> ( value ) -> (null)
• insertAt(value, index) inserts a new node with the provided value at the given index or at the end of the list if index is bigger than list size
• removeAt(index) removes the node at the given index or error message if the list is empty or if the request index is bigger than list size