# Element
Element is, quite simply, an abstraction layer atop [React](https://reactjs.org/).
You may find yourself asking, "Why an abstraction layer?". For a few reasons:
- In many applications, especially those extended by a rich plugin ecosystem as is the case with WordPress, it's wise to create interfaces to underlying third-party code. The thinking is that if ever a need arises to change or even replace the underlying implementation, it can be done without catastrophic rippling effects to dependent code, so long as the interface stays the same.
- It provides a mechanism to shield implementers by omitting features with uncertain futures (`createClass`, `PropTypes`).
- It helps avoid incompatibilities between versions by ensuring that every plugin operates on a single centralized version of the code.
On the `wp.element` global object, you will find the following, ordered roughly by the likelihood you'll encounter it in your code:
- [`createElement`](https://reactjs.org/docs/react-api.html#createelement)
- [`render`](https://reactjs.org/docs/react-dom.html#render)
## Installation
Install the module
```bash
npm install @wordpress/element --save
```
_This package assumes that your code will run in an **ES2015+** environment. If you're using an environment that has limited or no support for ES2015+ such as lower versions of IE then using [core-js](https://github.com/zloirock/core-js) or [@babel/polyfill](https://babeljs.io/docs/en/next/babel-polyfill) will add support for these methods. Learn more about it in [Babel docs](https://babeljs.io/docs/en/next/caveats)._
## Usage
Let's render a customized greeting into an empty element:
```html
```
Refer to the [official React Quick Start guide](https://reactjs.org/docs/hello-world.html) for a more thorough walkthrough, in most cases substituting `React` and `ReactDOM` with `wp.element` in code examples.
## Why React?
At the risk of igniting debate surrounding any single "best" front-end framework, the choice to use any tool should be motivated specifically to serve the requirements of the system. In modeling the concept of a [block](/packages/blocks/README.md), we observe the following technical requirements:
- An understanding of a block in terms of its underlying values (in the [random image example](/packages/blocks/README.md#example), a category)
- A means to describe the UI of a block given these values
At its most basic, React provides a simple input / output mechanism. **Given a set of inputs ("props"), a developer describes the output to be shown on the page.** This is most elegantly observed in its [function components](https://reactjs.org/docs/components-and-props.html#functional-and-class-components). React serves the role of reconciling the desired output with the current state of the page.
The offerings of any framework necessarily become more complex as these requirements increase; many front-end frameworks prescribe ideas around page routing, retrieving and updating data, and managing layout. React is not immune to this, but the introduced complexity is rarely caused by React itself, but instead managing an arrangement of supporting tools. By moving these concerns out of sight to the internals of the system (WordPress core code), we can minimize the responsibilities of plugin authors to a small, clear set of touch points.
## JSX
While not at all a requirement to use React, [JSX](https://reactjs.org/docs/introducing-jsx.html) is a recommended syntax extension to compose elements more expressively. Through a build process, JSX is converted back to the `createElement` syntax you see earlier in this document.
If you've configured [Babel](http://babeljs.io/) for your project, you can opt in to JSX syntax by specifying the `pragma` option of the [`transform-react-jsx` plugin](https://www.npmjs.com/package/babel-plugin-transform-react-jsx) in your [`.babelrc` configuration](http://babeljs.io/docs/usage/babelrc/).
```json
{
"plugins": [
[
"transform-react-jsx",
{
"pragma": "createElement"
}
]
]
}
```
This assumes that you will import the `createElement` function in any file where you use JSX. Alternatively, consider using the [`@wordpress/babel-plugin-import-jsx-pragma` Babel plugin](https://www.npmjs.com/package/@wordpress/babel-plugin-import-jsx-pragma) to automate the import of this function.
## API
# **Children**
Object that provides utilities for dealing with React children.
# **cloneElement**
Creates a copy of an element with extended props.
_Parameters_
- _element_ `WPElement`: Element
- _props_ `?Object`: Props to apply to cloned element
_Returns_
- `WPElement`: Cloned element.
# **Component**
A base class to create WordPress Components (Refs, state and lifecycle hooks)
# **concatChildren**
Concatenate two or more React children objects.
_Parameters_
- _childrenArguments_ `...?Object`: Array of children arguments (array of arrays/strings/objects) to concatenate.
_Returns_
- `Array`: The concatenated value.
# **createContext**
Creates a context object containing two components: a provider and consumer.
_Parameters_
- _defaultValue_ `Object`: A default data stored in the context.
_Returns_
- `Object`: Context object.
# **createElement**
Returns a new element of given type. Type can be either a string tag name or
another function which itself returns an element.
_Parameters_
- _type_ `?(string|Function)`: Tag name or element creator
- _props_ `Object`: Element properties, either attribute set to apply to DOM node or values to pass through to element creator
- _children_ `...WPElement`: Descendant elements
_Returns_
- `WPElement`: Element.
# **createInterpolateElement**
This function creates an interpolated element from a passed in string with
specific tags matching how the string should be converted to an element via
the conversion map value.
_Usage_
For example, for the given string:
"This is a string with a link and a self-closing
tag"
You would have something like this as the conversionMap value:
```js
{
span: ,
a: ,
CustomComponentB: ,
}
```
_Parameters_
- _interpolatedString_ `string`: The interpolation string to be parsed.
- _conversionMap_ `Object`: The map used to convert the string to a react element.
_Returns_
- `WPElement`: A wp element.
# **createPortal**
Creates a portal into which a component can be rendered.
_Related_
-
_Parameters_
- _child_ `import('./react').WPElement`: Any renderable child, such as an element, string, or fragment.
- _container_ `HTMLElement`: DOM node into which element should be rendered.
# **createRef**
Returns an object tracking a reference to a rendered element via its
`current` property as either a DOMElement or Element, dependent upon the
type of element rendered with the ref attribute.
_Returns_
- `Object`: Ref object.
# **findDOMNode**
Finds the dom node of a React component.
_Parameters_
- _component_ `import('./react').WPComponent`: Component's instance.
# **forwardRef**
Component enhancer used to enable passing a ref to its wrapped component.
Pass a function argument which receives `props` and `ref` as its arguments,
returning an element using the forwarded ref. The return value is a new
component which forwards its ref.
_Parameters_
- _forwarder_ `Function`: Function passed `props` and `ref`, expected to return an element.
_Returns_
- `WPComponent`: Enhanced component.
# **Fragment**
A component which renders its children without any wrapping element.
# **isEmptyElement**
Checks if the provided WP element is empty.
_Parameters_
- _element_ `*`: WP element to check.
_Returns_
- `boolean`: True when an element is considered empty.
# **isValidElement**
Checks if an object is a valid WPElement.
_Parameters_
- _objectToCheck_ `Object`: The object to be checked.
_Returns_
- `boolean`: true if objectToTest is a valid WPElement and false otherwise.
# **lazy**
_Related_
-
# **memo**
_Related_
-
# **Platform**
Component used to detect the current Platform being used.
Use Platform.OS === 'web' to detect if running on web enviroment.
This is the same concept as the React Native implementation.
_Related_
- Here is an example of how to use the select method:
_Usage_
```js
import { Platform } from '@wordpress/element';
const placeholderLabel = Platform.select( {
native: __( 'Add media' ),
web: __( 'Drag images, upload new ones or select files from your library.' ),
} );
```
# **RawHTML**
Component used as equivalent of Fragment with unescaped HTML, in cases where
it is desirable to render dangerous HTML without needing a wrapper element.
To preserve additional props, a `div` wrapper _will_ be created if any props
aside from `children` are passed.
_Parameters_
- _props_ `RawHTMLProps`: Children should be a string of HTML. Other props will be passed through to div wrapper.
_Returns_
- `JSX.Element`: Dangerously-rendering component.
# **render**
Renders a given element into the target DOM node.
_Parameters_
- _element_ `import('./react').WPElement`: Element to render.
- _target_ `HTMLElement`: DOM node into which element should be rendered.
# **renderToString**
Serializes a React element to string.
_Parameters_
- _element_ `import('react').ReactNode`: Element to serialize.
- _context_ `[Object]`: Context object.
- _legacyContext_ `[Object]`: Legacy context object.
_Returns_
- `string`: Serialized element.
# **StrictMode**
Component that activates additional checks and warnings for its descendants.
# **Suspense**
_Related_
-
# **switchChildrenNodeName**
Switches the nodeName of all the elements in the children object.
_Parameters_
- _children_ `?Object`: Children object.
- _nodeName_ `string`: Node name.
_Returns_
- `?Object`: The updated children object.
# **unmountComponentAtNode**
Removes any mounted element from the target DOM node.
_Parameters_
- _target_ `Element`: DOM node in which element is to be removed
# **useCallback**
_Related_
-
# **useContext**
_Related_
-
# **useDebugValue**
_Related_
-
# **useEffect**
_Related_
-
# **useImperativeHandle**
_Related_
-
# **useLayoutEffect**
_Related_
-
# **useMemo**
_Related_
-
# **useReducer**
_Related_
-
# **useRef**
_Related_
-
# **useState**
_Related_
-
