13 Feb 2024
In React.js, reconciliation is the process of comparing the virtual representation of a UI component (virtual DOM) with its previous state and determining what, if any, changes need to be applied to the actual DOM to reflect the new state. It efficiently updates the DOM to match the current component state while minimizing unnecessary re-renders and DOM manipulations.
When a component's state or props change, React will perform reconciliation to determine what changes need to be made to the DOM in order to reflect these updates. React's reconciliation algorithm, also known as the Virtual DOM diffing algorithm, compares the previous state of the virtual DOM with the new state and calculates the most efficient way to update the actual DOM.
Here's a basic overview of how reconciliation works in React:
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State or Prop Changes: When the state or props of a component change, React schedules an update to re-render the component.
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Reconciliation: React constructs a new virtual DOM tree representing the updated UI based on the changes in the component's state or props.
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Diffing Algorithm: React then compares the new virtual DOM tree with the previous one using a process called "diffing". It identifies the differences between the two trees efficiently.
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Update the DOM: After identifying the differences, React determines the minimal set of DOM mutations needed to update the actual DOM to reflect the changes in the virtual DOM.
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Re-rendering: React updates the actual DOM with the changes, ensuring that the UI reflects the updated state of the components.
Reconciliation helps React achieve high performance by minimizing the number of DOM manipulations required to update the UI, which leads to faster rendering and better user experience. However, it's essential to write components in a way that optimizes reconciliation by ensuring that components are kept as simple and pure as possible, avoiding unnecessary re-renders, and leveraging techniques like PureComponent, useMemo, and useCallback when necessary.
