pop() {
    if (this.length === 1) {
      this.top = null;
      this.bottom = null;
    } else {
      const node = this.top.next;
      this.top = node;
    }
    this.length--;
    return this;
  }
/**
   * remove from top of stack
   *
   * @returns
   * @memberof Stack
   */
remove from top of stack
@returns
@memberof Stack
remove from top of stack @returns @memberof Stack
pop() {
    if (this.length === 1) {
      this.top = null;
      this.bottom = null;
    } else {
      const node = this.top.next;
      this.top = node;
    }
    this.length--;
    return this;
  }
pop ( ) { if ( this . length === 1 ) { this . top = null ; this . bottom = null ; } else { const node = this . top . next ; this . top = node ; } this . length -- ; return this ; }
remove from top of stack
 @returns
 @memberof Stack
remove from top of stack @returns @memberof Stack