Understanding React Fiber

React Fiber is a complete overhaul of React’s reconciliation engine, making the UI updates more efficient. It breaks down rendering work into smaller units, allowing React to manage rendering tasks more effectively, even when interruptions occur. In this blog, we’ll dive into how it operates and explore a code example that demonstrates its power.

What is React Fiber?

It optimizes the rendering process by dividing tasks into chunks, enabling React to pause, prioritize, or stop rendering as needed. Before Fiber, it used a “stack-based” algorithm, which could result in blocking, making the UI unresponsive during complex updates. Now, React Fiber makes the rendering process more adaptable, ensuring smoother experiences.

How Does It Work?

It works in two phases: the “render phase” and the “commit phase.” During the render phase, React creates a tree of work in progress, allowing tasks to be interrupted and resumed. Then, the commit phase updates the DOM, which happens in a single pass.

Let’s see an example:

import React, { useState } from 'react';

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

  const handleIncrement = () => {
    setCount(count + 1);
  };

  const handleHeavyCalculation = () => {
    let sum = 0;
    for (let i = 0; i < 1000000000; i++) {
      sum += i;
    }
    return sum;
  };

  return (
    <div>
      <h2>Count: {count}</h2>
      <button onClick={handleIncrement}>Increment</button>
      <p>Result of heavy calculation: {handleHeavyCalculation()}</p>
    </div>
  );
};

export default Counter;

 

In this example, it handles the heavy calculation without freezing the UI, ensuring smooth counter updates. Although the handleHeavyCalculation function seems intense, It manages to break the task into manageable chunks, which helps maintain performance.

 

Summarize:

React Fiber enhances rendering efficiency. With this new reconciliation engine, developers can create more responsive and fluid UIs, regardless of complexity.