Class LinkedList

chapter02/util/LinkedListX.js:23–138

  }
  
  class LinkedList {
    constructor() {
        this.head = null;
        this.tail = null;
    }
  
    append(value) {
        let node = new Node(value);
        // if list is empty
        if (!this.head) {
            this.head = node;
            this.tail = node;
        }
        else {
            this.tail.next = node;
            this.tail = node;
        }
    }
  
    prepend(value) {
        let node = new Node(value);
        node.next = this.head;
        this.head = node;
    }
  
    pop() {
        let cur = this.head;
  
        // only one or no item exists
        if (!cur) return null;
        if (!cur.next) {
            this.head = null;
            return cur;
        }
        // move till the 2nd last
        while (cur.next.next)
            cur = cur.next;
        
        let last = this.tail;
        this.tail = cur;
        this.tail.next = null;
        return last;
    }
  
    popFirst() {
        let first = this.head;
        if (this.head && this.head.next) {
            this.head = this.head.next;
            first.next = null;
        }
        else this.head = null;
        return first;
    }
  
    head() {
        return this.head;
    }