Method push

source/list.js:23–34

(item)

  }

  push(item) {
    const link = makeLink(item);
    if (this.isEmpty) {
      this.start = link;
      this.end = link;
      this.isEmpty = false;
    } else {
      this.end.next = link;
      link.previous = this.end;
      this.end = link;
    }
  }

  pop() {
    if (this.isEmpty) {