Optimize page performance: Solve slow page loading problems caused by redrawing and reflowing

Improve page loading speed: To solve the performance bottleneck caused by page redrawing and reflow, specific code examples are needed

With the development of the Internet, users are increasingly concerned about web page loading speed The requirements are getting higher and higher. Page loading speed is directly related to user experience and evaluation of the website, so for developers, improving page loading speed is a very important task. Page redraws and reflows are one of the main causes of slow page loading. This article will detail the reasons for page redrawing and reflow and how to reduce the performance bottlenecks caused by them through code optimization.

First of all, we need to understand the concepts of page redrawing and reflow.

Page redrawing means that when the elements in the page need to change their style, the browser will redraw these elements. Page reflow means that when elements on the page change position, size, content, etc., the browser needs to recalculate the position and size of the elements and then redraw these elements.

Page redrawing and reflow require the browser to re-render the page. This process is very performance-consuming. Therefore, we need to optimize the code to reduce the number of page redraws and reflows, thereby improving page loading speed.

The following are several common optimization tips:

1. Reduce operations on the DOM

When the page changes size, position or triggers animation, it will cause Page reflow. Therefore, we should try to reduce operations on the DOM and try to merge multiple operations into one.

For example, if we need to change the width and height of an element, we can hide it first, then change the size, and finally display it.

// Bad
element.style.width = '100px';
element.style.height = '100px';

// Good
element.style.display = 'none';
element.style.width = '100px';
element.style.height = '100px';
element.style.display = 'block';

2. Avoid frequent access to the style attribute

Frequent access to the style attribute will also cause page reflow. Therefore, we should try to avoid frequently accessing the style attribute in JavaScript.

// Bad
for (let i = 0; i < elements.length; i++) {
  elements[i].style.width = '100px';
  elements[i].style.height = '100px';
}

// Good
const width = '100px';
const height = '100px';
for (let i = 0; i < elements.length; i++) {
  elements[i].style.width = width;
  elements[i].style.height = height;
}

3. Using document fragments

When multiple DOM elements need to be created dynamically, we can use document fragments to improve performance. A document fragment is a lightweight container into which multiple DOM elements can be added and then inserted into the document all at once.

// Bad
for (let i = 0; i < 1000; i++) {
  const element = document.createElement('div');
  document.body.appendChild(element);
}

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

4. When using animation effects, use transform to replace top/left

When using animation effects, use transform to replace top/left and other attributes to avoid page reflow.

.element {
  transform: translate(100px, 100px);
}

/* Bad */
.element {
  top: 100px;
  left: 100px;
}

/* Good */
.element {
  transform: translate(100px, 100px);
}

Through the above optimization techniques, we can reduce the number of page redraws and reflows, thereby improving page loading speed. Of course, there are many other optimization techniques. Different projects may have different optimization methods. Developers can choose the appropriate optimization method according to the actual situation.

In summary, by reducing operations on the DOM, avoiding frequent access to the style attribute, using document fragments, and using transform instead of top/left and other attributes, we can greatly reduce the number of page redraws and reflows. , thereby improving page loading speed. At the same time, optimizing page loading speed is also an important means to improve user experience. Developers should pay attention to this and focus on performance optimization during the development process.

The above is the detailed content of Optimize page performance: Solve slow page loading problems caused by redrawing and reflowing. For more information, please follow other related articles on the PHP Chinese website!