No, React does not re-render all components and sub-components every time setState is called. Instead, React updates the state of the component and then re-renders only the components that are affected by the state change. This selective re-rendering is part of React's efficient update mechanism, which aims to only make changes to the DOM when necessary, thus optimizing performance.
When setState is called, React schedules an update to the component's state and marks it as dirty, meaning the component needs to be re-rendered. However, before re-rendering, React performs a reconciliation process where it compares the new return value of the render function to the previous one. During this process, React uses a diffing algorithm to determine which parts of the DOM need to be updated. This is done to minimize the amount of DOM manipulation required, which is a costly operation.
Furthermore, developers can control this behavior using the shouldComponentUpdate lifecycle method in class components or React.memo for functional components. These allow the developer to add custom logic to decide whether a component should ...
