Optimization strategy: The best reflow and redraw method to improve page loading speed

Reduce page load time: Best reflow and repaint optimization strategies, specific code examples required

With the development of the Internet, web pages have become the place where people obtain information and communicate is an important platform, and page loading time has become an important indicator that affects user experience. A web page that takes too long to load will not only turn away users, but it can also lower your website’s conversion rate and search engine rankings. Therefore, how to reduce page loading time has become the focus of developers.

In the process of optimizing page load time, the best reflow and redraw optimization strategies can effectively improve the performance of web pages. Reflow and repaint are two important steps when the browser renders the page. Reflow refers to the process of calculating the page layout and element positions, while redrawing refers to the process of drawing the page based on the calculation results. Both processes are time-consuming operations, so optimizing for them can greatly improve page loading speed.

The following are some of the best reflow and redraw optimization strategies, as well as corresponding code examples:

1. Use the transform attribute to replace top, left and other attributes
   When we use top , left and other attributes to change the position of the element, the reflow operation will be triggered. The transform attribute can be used to change the position of the element without triggering reflow. The following is a sample code:

// 不优化的写法
element.style.top = '100px';
element.style.left = '200px';

// 优化的写法
element.style.transform = 'translate(200px, 100px)';

2. Use visibility attribute instead of display:none
   When we set the display attribute of an element to none, reflow and redraw operations will be triggered. Using the visibility attribute to hide elements can only trigger the redraw operation. The following is a sample code:

// 不优化的写法
element.style.display = 'none';

// 优化的写法
element.style.visibility = 'hidden';

3. Use DocumentFragment to reduce DOM operations
   Frequent DOM operations will also cause frequent triggering of reflow and redraw. You can use DocumentFragment to create a document fragment, concentrate DOM operations in the document fragment, and finally insert it into the document at once. The following is a sample code:

// 不优化的写法
for (let i = 0; i < 1000; i++) {
  const element = document.createElement('div');
  document.body.appendChild(element);
}

// 优化的写法
const fragment = document.createDocumentFragment();
for (let i = 0; i < 1000; i++) {
  const element = document.createElement('div');
  fragment.appendChild(element);
}
document.body.appendChild(fragment);

4. Use CSS animation instead of JavaScript animation
   When implementing animation effects, using CSS animation is more efficient than using JavaScript animation. Because CSS animation is drawn at the rendering level, JavaScript animation needs to be implemented through communication between the JS engine and the rendering engine. The following is a sample code:

/* 不优化的写法 */
.element {
  position: absolute;
  left: 0;
  top: 0;
  transition: left 1s linear;
}
.element:hover {
  left: 100px;
}

/* 优化的写法 */
@keyframes move {
  from {
    left: 0;
  }
  to {
    left: 100px;
  }
}
.element {
  position: absolute;
  left: 0;
  top: 0;
  animation: move 1s linear;
}

Through the above optimization strategies, we can greatly improve the page loading speed. Of course, different pages have different optimization needs, and the specific optimization strategies may also be different. But in general, minimizing reflow and redraw operations, clustering DOM operations together, and using appropriate animation methods can effectively increase page loading speed and improve user experience.

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