How the React Virtual DOM Works

The Virtual DOM (Document Object Model) in React is a programming concept where a lightweight, in-memory representation of the actual DOM is created. The main purpose of the Virtual DOM is to improve the efficiency of updating the user interface by minimizing direct manipulations of the actual DOM.

Here's an overview of how the React Virtual DOM works:

1. Initial Render:

   • When a react component is initially rendered or updated, it first creates a virtual DOM representation of the UI components and their structure.

   • This representation is a tree-like structure that mirrors the structure of the actual DOM

2. JSX and React Elements:

   • JSX code is written in the React component, defining the structure of the UI.

   • Each JSX element is converted into a corresponding React element, which is a plain JavaScript object representing a DOM node.

3. Reconciliation:

   • When there is a change in the component's state or props, React creates a new Virtual DOM tree.

   • This new tree is then compared with the previous Virtual DOM tree using a process called reconciliation.

4. Differential Algorithm:

   • React uses a reconciliation algorithm (also known as the "diffing" algorithm) to identify differences between the new Virtual DOM tree and the previous one.

   • The algorithm efficiently determines which parts of the Virtual DOM have changed, been added, or been removed.

5. Minimizing DOM Manipulations:

   • Once the differences are identified, React generates a minimal set of changes needed to update the actual DOM.

   • Instead of updating the entire DOM, React only applies the specific changes required to bring the actual DOM in sync with the new Virtual DOM.

6. Batched Updates:

   • React optimizes the process by batching multiple updates together.

   • Updates are not immediately applied to the actual DOM; instead, React queues them up and performs a batched update, minimizing the number of times the real DOM is manipulated.

7. Efficient Rendering:

   • After determining the minimal set of changes, React efficiently applies these changes to the real DOM, updating only the parts that have changed.

   • This approach significantly reduces the time and resources needed for rendering, making the UI updates more performant.

8. Event Delegation:

   • React uses event delegation to handle user interactions.

   • Instead of attaching event listeners to individual elements, React utilizes a single event listener at a higher level (e.g., the document level) and delegates events to the appropriate components.

By using the Virtual DOM and the differential reconciliation algorithm, React minimizes direct manipulations of the actual DOM, leading to more efficient and optimized UI updates. This process contributes to React's ability to create dynamic and responsive user interfaces with improved performance.