A brief discussion on how React components will be re-rendered

When we write components using React, re-rendering of components is an important concept. Re-rendering means that React components will re-execute their rendering functions in a specific situation, updating the user interface to reflect the latest data. In many cases, unnecessary re-rendering of components will seriously affect performance, so you must fully understand the conditions that trigger re-rendering of components.

Props Changes

In React, the props of a component are the data passed to the child component by the parent component. When these props change, the subcomponent will be re-rendered to reflect the latest data.

// Parent componentconst ParentComponent = () => {
  const [value, setValue] = useState(0);

  return <ChildComponent prop={value} />;
};

// Subcomponentsconst ChildComponent = (({ prop }) => {
  // When the prop changes, re-rendering will be triggered  return <p>{prop}</p>;
});

State Changes

The state in React is managed through useState. When the state is updated using the setState function, the component will be re-rendered.

const Counter = () => {
  const [count, setCount] = useState(0);

  const increment = () => {
    setCount(count + 1); // When count changes, component re-renders  };

  return (
    <div>
      <p>{count}</p>
      <button onClick={increment}>Increment</button>
    </div>
  );
};

Context Changes

React Context allows us to pass data in the component tree without having to pass it manually one level at a time. When the value of the Context changes, components subscribed to that Context will be re-rendered.

const MyComponent = () => {
  const contextValue = useContext(MyContext); // When the value of MyContext changes, the component re-renders
  // ...
};

Using forceUpdate

While forceUpdate is not recommended, in some cases you may need to force component re-rendering. The forceUpdate method will cause the component's render method to be called.

const MyComponent = () => {
  const forceUpdate = useForceUpdate();

  const handleClick = () => {
    // Force component re-rendering    forceUpdate();
  };

  // ...
};

Parent component re-renders

When a child component is nested in a parent component, the parent component re-renders and the child component is re-rendered.

const ParentComponent = () => {
  // Status variable count  const [count, setCount] = useState(0);

  return (
    <div>
      <p>Parent Component Count: {count}</p>
      <ChildComponent />
      <button onClick={() => setCount(count + 1)}>Increment Parent</button>
    </div>
  );
};

// Subcomponentsconst ChildComponent = () => {
  ("Child Component Rendered");

  return <p>Child Component</p>;
};

Summarize

These cases cover the main scenarios that result in the re-rendering of React functional components. React detects these changes through virtual DOM, enabling efficient updates to ensure that the user interface remains up to date. Understanding these re-rendering situations helps us better optimize and design React applications.

This is the end of this article about the situation where React components will be re-rendered. For more related React re-rendering content, please search for my previous articles or continue browsing the related articles below. I hope everyone will support me in the future!