Reactjs Does Render Get Called Any Time Setstate Is Called

In React.js, the question of whether the `render` method gets called every time `setState` is called is a common query that arises among developers. Let's dive into the workings of React.js to understand this aspect more clearly.

When a component's state changes in React.js, the `render` method is not called immediately. Instead, React batches state updates for better performance. This means that calling `setState` multiple times within the same synchronous block of code will only trigger a single re-render at the end of it.

So, to answer the question: "Does `render` get called every time `setState` is called?" The answer is no, it doesn't. It gets called only once per batched update process. This batching mechanism ensures that React efficiently updates the component's UI without unnecessary re-renders.

However, there are scenarios where you might need to perform additional actions after the state has been updated and the component has re-rendered. For such cases, React provides the `componentDidUpdate` lifecycle method.

The `componentDidUpdate` method is invoked immediately after the component updates and the `render` method has been called. It receives the previous props and state as arguments, allowing you to compare them and perform side effects based on the state changes.

Here's an example to illustrate this concept:

class MyComponent extends React.Component {
  state = {
    count: 0,
  };

  handleClick = () => {
    this.setState({ count: this.state.count + 1 });
  };

  componentDidUpdate(prevProps, prevState) {
    if (this.state.count !== prevState.count) {
      console.log('Count updated: ', this.state.count);
    }
  }

  render() {
    return (
      <div>
        <p>Count: {this.state.count}</p>
        <button>Increment</button>
      </div>
    );
  }
}

In this example, every time the "Increment" button is clicked, the `count` state is updated, causing the component to re-render. The `componentDidUpdate` method then logs the updated count value to the console.

Understanding when and how the `render` method is invoked in React.js is crucial for optimizing performance and managing side effects effectively in your applications. By leveraging lifecycle methods like `componentDidUpdate`, you can respond to state changes and update the UI accordingly.

In conclusion, while `render` does not get called every time `setState` is invoked due to React's batching mechanism, you can use lifecycle methods like `componentDidUpdate` to handle post-update logic and ensure your components respond appropriately to state changes.