In React, rendering refers to the process of converting your React components into a visual representation on the screen. The rendering process in React follows a series of steps. Let's go through them step by step:
Component Hierarchy: In React, your application is typically organized into a hierarchy of components. At the top of this hierarchy is usually a root component, which represents the entire application. This root component can contain other components, which in turn can contain more components, forming a tree-like structure.
Virtual DOM: React uses a virtual representation of the actual browser DOM called the Virtual DOM. It's a lightweight copy of the real DOM, stored in memory. When a React component is rendered, it creates a corresponding virtual representation of that component and its children.
Initial Render: When you initially load your React application, React starts the rendering process by calling the
rendermethod on the root component. This triggers the creation of the virtual DOM for that component and its children.Diffing Algorithm: After the initial render, React performs a process called reconciliation or diffing. It compares the previous virtual DOM with the new one generated during the render process to determine the minimal set of changes needed to update the actual DOM.
Update the DOM: Once React determines the differences between the previous and new virtual DOM, it applies those changes to the actual browser DOM. It updates only the necessary parts of the DOM tree, minimizing the impact on performance.
Lifecycle Methods: During the rendering process, React also invokes a series of lifecycle methods on the components. These methods allow you to perform additional logic at specific points in the component's lifecycle, such as before it is rendered, after it is rendered, or when it is about to be removed from the DOM.
Re-rendering: In React, components can be re-rendered whenever their state or props change. When a component's state or props are updated, React triggers the re-rendering process for that component and its children. It creates a new virtual DOM representation, compares it with the previous one, and updates the actual DOM accordingly.
Component Updates: React optimizes the rendering process by intelligently updating only the parts of the component tree that have changed. This avoids unnecessary re-rendering of unaffected components, improving performance.
By following this step-by-step process, React efficiently updates the user interface, ensuring that it remains in sync with the underlying data and state of your application.