Here are the frequently asked questions about Ant Design and antd that you should look up before you ask in the community or create a new issue. We also maintain a [FAQ issues label](http://u.ant.design/faq) for common github issues.
**Yes. antd will treats `undefined` as uncontrolled but `null` as controlled components which means empty value of it.**
As input element, React treats both `undefined` and `null` as uncontrolled. When the `value` is converted from a valid value to `undefined` or `null`, the component is no longer controlled, which causes some unexpected cases.
But in antd, `undefined` is treated as uncontrolled, and `null` is used as an explicit empty value of controlled components. To deal with some cases (e.g. `allowClear`) like clearing the `value` when the `value` is non-primitive. If you need a component controlled with the `value` valid, just set the `value` as `null`.
Note: For `options` in `Select-like` components, it is **strongly recommended not** to use `undefined` and `null` as `value` in `option`. Please use `string | number` as a valid `value` in `option`.
## Can I use internal API which is not documented on the site?
NOT RECOMMEND. Internal API is not guaranteed to be compatible with future versions. It may be removed or changed in some versions. If you really need to use it, you should to make sure these API is still valid when upgrading to a new version or just lock version for usage.
We are cautious when adding APIs because some APIs may not be abstract enough to become historical debt. For example, when there is a need to change the way of interaction, these poor abstractions may cause breaking changes. To avoid such problems, we recommend that new features be implemented through HOCs first.
This is an old bug that has been fixed since `v3.11.x`. If you're using an older version, you can use `<Select getPopupContainer={trigger => trigger.parentElement}>` to render a component inside Popover. (Or other `getXxxxContainer` props)
Use `<Select getPopupContainer={trigger => trigger.parentElement}>` ([API reference](/components/select/#Select-props)) to render a component inside the scroll area. If you need to config this globally in your application, try `<ConfigProvider getPopupContainer={trigger => trigger.parentElement}>` ([API reference](/components/config-provider/#API))
While you can override a component's style, we don't recommend doing so. antd is not only a set of React components, but also a design specification as well.
The `defaultXxxx` (e.g. `defaultValue`) of `Input`/`Select`(etc...) only works on the first render. It is a specification of React. Please read [React's documentation](https://facebook.github.io/react/docs/forms.html#controlled-components).
antd use shallow compare of props to optimize performance. You should always pass the new object when updating the state. Please ref [React's document](https://reactjs.org/docs/thinking-in-react.html)
Yes, antd is designed to help you develop a complete background application. To do so, we override some global styles for styling convenience, and currently these cannot be removed or changed. More info at https://github.com/ant-design/ant-design/issues/4331 .
Please check [Ant Design Mobile](http://mobile.ant.design) as a possible solution, as `antd` has not been optimized to work well on mobile. You can also try the [react-component](https://github.com/react-component/) repositories which start with 'm-' 'rn-', which are also designed for mobile.
Yes, you can [import `antd` with script tag](https://ant.design/docs/react/introduce#Import-in-Browser), but we recommend using `npm` to import `antd`, as it is simple and easy to maintain.
If you need some features which should not be included in antd, try to extend antd's component with [HOC](https://gist.github.com/sebmarkbage/ef0bf1f338a7182b6775). [more](https://medium.com/@dan_abramov/mixins-are-dead-long-live-higher-order-components-94a0d2f9e750#.eeu8q01s1)
antd 会透出组件定义，但是随着重构可能导致内部一些定义命名或者属性变化。因而更推荐直接使用 Typescript 原生能力获取： antd will export mainly definitions, but not export internal definitions which may be rename or changed. So we recommend you to use Typescript's native ability to get the definition if needed:
```tsx
import { Table } from 'antd';
type Props<Textends(...args:any)=> any> = Parameters<T>[0];
If you are using a mismatched version of dayjs with [antd's dayjs](https://github.com/ant-design/ant-design/blob/7dfc80504a36cf8952cd732a1d0c137a16d56fd4/package.json#L125) in your project. That would be a problem cause locale not working.
In a real world development, you may need a `YearPicker`, `MonthRangePicker` or `WeekRangePicker`. You are trying to add `mode` to `DatePicker`/`RangePicker` expected to implement those pickers. However, the `DatePicker`/`RangePicker` cannot be selected and the panels won't close now.
Like [the explanation](https://github.com/ant-design/ant-design/issues/11586#issuecomment-429189877) explains, this is because `<DatePicker mode="year" />` does not equal the `YearPicker`, nor is `<RangePicker mode="month" />` equal to `MonthRangePicker`. The `mode` property was added to support [showing time picker panel in DatePicker](https://github.com/ant-design/ant-design/issues/5190) in antd 3.0, which simply controls the displayed panel, and won't change the original date picking behavior of `DatePicker`/`RangePicker` (for instance you will still need to click date cell to finish selection in a `DatePicker`, whatever the `mode` is).
Likewise，`disabledDate` [cannot work on year/month panels](https://github.com/ant-design/ant-design/issues/9008#issuecomment-358554118) of `<DatePicker mode="year/month" />`, but only on cells of date panel.
You can refer to [this article](https://juejin.im/post/5cf65c366fb9a07eca6968f9) or [this article](https://www.cnblogs.com/zyl-Tara/p/10197177.html), using `mode` and `onPanelChange` to encapsulate a `YearPicker` or `MonthRangePicker` for your needs.
Or you can simply upgrade to [antd@4.0](https://github.com/ant-design/ant-design/issues/16911), in which we [added more XxxPickers](https://github.com/ant-design/ant-design/issues/4524#issuecomment-480576884) to meet those requirements, and `disabledDate` could be effect on those pickers too.
Static methods like message/notification/Modal.confirm are not using the same render tree as `<Button />`, but rendered to independent DOM node created by `ReactDOM.render`, which cannot access React context from ConfigProvider. Consider two solutions here:
1. Replace original usages with [message.useMessage](/components/message/#components-message-demo-hooks), [notification.useNotification](/components/notification/#Why-I-can-not-access-context,-redux,-ConfigProvider-locale/prefixCls-in-notification) and [Modal.useModal](/components/modal/#Why-I-can-not-access-context,-redux,-ConfigProvider-locale/prefixCls-in-Modal.xxx).
You should only access the API by official doc with ref. Directly access internal `props` or `state` is not recommended which will make your code strong coupling with current version. Any refactor will break your code like refactor with [Hooks](https://reactjs.org/docs/hooks-intro.html) version, delete or rename internal `props` or `state`, adjust internal node constructor, etc.
## Why we need align pop component with `open` prop?
For historical reasons, the display names of the pop components are not uniform, and both `open` and `visible` are used. This makes the memory cost that non-tsx users encounter when developing. It also leads to ambiguity about what name to choose when adding a feature. So we want to unify the attribute name, you can still use the original `visible` and it will still be backward compatible, but we will remove this attribute from the documentation as of v5.
