Method shift

source/list.js:52–66

()

  }

  shift() {
    if (this.isEmpty) {
      return undefined;
    }

    const item = this.start.item;
    if (this.start === this.end) {
      this.clear();
      return item;
    }

    this.start = this.start.next;
    this.start.previous = undefined;
    return item;
  }

  clear() {
    this.start = undefined;