Optimize code: ways to reduce reflow and redraw

Part 1: Streamlined code implementation: Tips to reduce reflow and redraw

When developing web applications, optimizing performance is an important task. Among them, reducing page reflow (reflow) and repaint (repaint) is one of the key points to improve web page performance. This article will share some tips and specific code examples to help you better reduce reflows and redraws and improve the performance of web pages.

1. Use CSS3 animation instead of JavaScript animation

On elements that require animation effects, try to use CSS3 animation instead of implementing animation through JavaScript. CSS3 animations utilize hardware acceleration, which effectively reduces reflows and redraws. The following is an example of using CSS3 animation:

.animated-element {
  transform: translateX(0);
  transition: transform 0.3s;
}

.animated-element:hover {
  transform: translateX(100px);
}

2. Batch operation style

When making multiple style modifications to an element, we can combine these operations into one Batch operation, one-time style modification by changing the element's className or using classList. This reduces the number of reflows and redraws. The following is an example of using classList:

element.classList.add('class1', 'class2');
element.classList.remove('class3');

3. Using throttling and anti-shake

When listening to browser events, for some frequently triggered For events such as scroll and resize, we can use throttling and debounce to reduce the number of reflows and redraws. Throttling and anti-shake can be achieved through custom functions or using third-party libraries. The following is an example of throttling and anti-shaking using the lodash library:

// 节流
window.addEventListener('scroll', _.throttle(function() {
  // 需要执行的代码
}, 200));

// 防抖
window.addEventListener('resize', _.debounce(function() {
  // 需要执行的代码
}, 300));

4. Using virtual DOM

Virtual DOM (Virtual DOM) is a method of converting page elements into The update operation is first applied to the virtual DOM tree, then compared with the real DOM, and finally only the parts that really need to be updated are updated, thereby reducing the overhead of reflow and redrawing. Commonly used virtual DOM libraries include React and Vue. The following is an example using React:

class MyComponent extends React.Component {
  render() {
    return (
      <div>
        {/* 内容 */}
      </div>
    );
  }
}

ReactDOM.render(<MyComponent />, document.getElementById('root'));

5. Using requestAnimationFrame

Using requestAnimationFrame for animation drawing, you can The browser executes the JavaScript code before the next redraw, thus consolidating multiple redraws into one. The following is an example of using requestAnimationFrame:

function render() {
  // 绘制代码

  requestAnimationFrame(render);
}

render();

Through some of the above simple techniques and specific code examples, we can effectively reduce the number of reflows and redraws and improve the performance of web applications . I hope this content can be helpful to your web page optimization work.

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