React handles rendering through a process called the Virtual DOM (Document Object Model). Here’s a simplified overview of how it works:
Below are main points for rendering
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Component Hierarchy
In React, UI is built using components, which are essentially JavaScript classes or functions are a reusable piece of code. These components are organized into a tree-like structure, with each component representing a part of the UI.
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Initial Render
When a React application starts up, or when a component is first rendered, React constructs a virtual representation of the DOM, known as the Virtual DOM. This Virtual DOM is a lightweight, in-memory representation of the actual DOM.
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State and Props
Components in React can have both state and props. State represents the internal data of a component that can change over time, while props are immutable data passed from parent to child components.
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Reconciliation
When the state of a component changes, or when new props are passed to a component, React triggers a process called reconciliation. During reconciliation, React compares the new virtual DOM representation with the previous one to determine what has changed.
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Diffing Algorithm
React uses a reconciliation algorithm to efficiently determine the differences (or “diffs”) between the new virtual DOM tree and the previous one. This process is called “diffing”. React employs a highly efficient diffing algorithm to identify the differences between the new virtual DOM and the previous one. This algorithm minimizes the number of actual DOM manipulations required to update the UI.
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Minimal Updates
React then applies only the necessary changes to the actual DOM to bring it in sync with the virtual DOM. This minimizes the number of DOM manipulations, which can be costly in terms of performance. Once the differences are identified, React calculates the minimum set of DOM mutations needed to bring the actual DOM in sync with the new virtual DOM. This approach reduces the performance overhead associated with directly manipulating the DOM.
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Updating the DOM
Finally, React updates the real DOM with the changes identified during the diffing process. This update is done in a batched manner for performance reasons.
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Batched Updates
React batches multiple DOM updates into a single operation to optimize performance. This means that multiple changes triggered by state updates within the same event loop iteration are combined into a single update to the DOM.
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Rendering Optimization
React also provides mechanisms for optimizing rendering performance, such as shouldComponentUpdate lifecycle method, PureComponent, and React.memo for functional components. These tools allow developers to prevent unnecessary re-renders of components when their props or state haven’t changed.
By using this Virtual DOM and reconciliation process, React is able to efficiently update the UI in response to changes in state or props, resulting in a more responsive and performant web application.
