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ReactDOM

ReactDOM is a library that acts as the glue between React components and the DOM (Document Object Model). It provides a set of APIs to manipulate and interact with the DOM, allowing you to render React components into web pages and manage their lifecycle. Here are some of the key features and methods provided by ReactDOM:

Features​

Virtual DOM​

One of the most significant features of ReactDOM is its use of a Virtual DOM. This is an in-memory representation of the actual DOM elements. The rendering engine can quickly make changes to the Virtual DOM and then subsequently update the DOM in a more optimized and efficient way.

Reconciliation​

ReactDOM uses a reconciliation algorithm to find the most efficient way to update the DOM. When a component's state or props change, ReactDOM creates a new Virtual DOM tree and compares it with the old one, updating only the changed parts in the actual DOM.

Event Handling​

ReactDOM normalizes event handling by wrapping the browser's native events into synthetic events, providing a consistent API across different browsers.

Key Methods​

ReactDOM.render()​

This is the most commonly used ReactDOM method. It renders a React element into a DOM node. If the React element was previously rendered into the container, this method performs an update on it and only changes the DOM to reflect the latest React element.

ReactDOM.render(<App />, document.getElementById('root'));

ReactDOM.unmountComponentAtNode()​

This method removes a mounted React component from the DOM and cleans up its event handlers and state. If no component was mounted in the container, calling this function does nothing.

ReactDOM.unmountComponentAtNode(document.getElementById('root'));

ReactDOM.createPortal()​

This method creates a portal. Portals provide a way to render children into a DOM node that exists outside the DOM hierarchy of the parent component.

ReactDOM.createPortal(child, container);

ReactDOM.hydrate()​

This method is similar to render(), but it is used for hydrating a container whose HTML contents were rendered by ReactDOMServer. Hydration enables a client-side React application to take over an existing server-rendered app.

ReactDOM.hydrate(<App />, document.getElementById('root'));

ReactDOM.findDOMNode()​

This method returns the native DOM element if the component has been rendered into the DOM. Note that this method is considered legacy and should be avoided in favor of other techniques like refs.

const domNode = ReactDOM.findDOMNode(this);

Understanding ReactDOM is crucial for effectively working with React, as it provides the essential functionalities for rendering and updating the UI. It offers a range of methods and features that make it easier to build dynamic and interactive web applications.