JavaScript 数组：判断数组中是否有重复项

  const checkArrayDuplication = rowHeaderArr.map((element: string) => {
    if (header !== '') {
      const firstIndex = rowHeaderArr.indexOf(element);
      const lastIndex = rowHeaderArr.lastIndexOf(element);
      if (firstIndex !== lastIndex) {
        // antd notification
        notification.error({
          description: '',
          message: '重复！',
        });
        return 'notSave';
      }
    }
    return 'save';
  });

Array.prototype.indexOf() - JavaScript | MDN (mozilla.org)