How to reduce reflows and redraws

Methods to reduce reflow and redraw include using CSS3 animation and transition effects, using transform and opacity attributes, avoiding frequent DOM operations, using event delegation, using virtual DOM, using CSS will-change attributes, using requestAnimationFrame, etc. . Detailed introduction: 1. Use CSS3 animations and transition effects. CSS3 provides some powerful animations and transition effects, which can be used to replace JavaScript to achieve animation effects and so on.

The operating system for this tutorial: Windows 10 system, DELL G3 computer.

In modern web development, reflow and repaint are two aspects that need to be focused on in performance optimization. Reflow and redraw are two important steps when a browser renders a page. Their frequent occurrence will lead to a decrease in page performance and affect the user experience. Therefore, reducing reflows and redraws is one of the keys to optimizing web page performance. This article will introduce some techniques to reduce reflow and redraw to help developers improve web page performance.

First of all, we need to understand the concepts of reflow and redraw. Reflow refers to the process that occurs when the browser needs to recalculate the position and geometric properties of an element. For example, when changing the size, position, font and other attributes of an element, the browser will trigger a reflow operation. Redrawing refers to the process in which the browser needs to redraw the element when its appearance changes. Reflow and redraw are very resource-intensive operations, so we need to minimize their occurrence.

Here are some tips to reduce reflow and redraw:

1. Use CSS3 animations and transition effects: CSS3 provides some powerful animations and transition effects that can be used to implement animations instead of JavaScript. Effect. Because CSS3 animations and transitions are performed within the browser's rendering engine, they do not trigger reflows and repaints, improving performance.

2. Use transform and opacity attributes: When you need to change the position and size of an element, you can use the transform attribute instead of changing the top, left, width and height attributes of the element. The transform attribute is performed in the GPU and does not trigger reflow or redraw. In addition, when you need to change the transparency of an element, you can use the opacity attribute, which will not trigger reflow and redraw.

3. Avoid frequent DOM operations: DOM operations are very resource-consuming, especially when the position and size of elements need to be changed. Therefore, we should try to avoid frequent DOM manipulation. You can use DocumentFragment to insert or delete multiple elements in batches, or use string concatenation to generate HTML fragments and then insert them into the DOM at once.

4. Use event delegation: When you need to add the same event handler to multiple elements, you can add the event handler to their common parent element, and then handle the event through the event bubbling mechanism. This reduces the number of event handlers, thus reducing the occurrence of reflows and redraws.

5. Use virtual DOM: Virtual DOM is a technology that abstracts the state of the page into a JavaScript object, which can be operated on the JavaScript level, and then the changes are applied to the real DOM. Virtual DOM can update DOM in batches, reducing the occurrence of reflow and redrawing.

6. Use the CSS will-change attribute: The will-change attribute can tell the browser the changes that will occur to the element, allowing the browser to prepare for optimization in advance. For example, when we know that the position of an element is about to change, we can use will-change: transform to tell the browser, so that the browser can optimize it when rendering.

7. Use requestAnimationFrame: requestAnimationFrame is an API provided by the browser to optimize animation effects. It allows the browser to execute the specified function before the next redraw, thereby ensuring the smoothness of the animation.

Through the above techniques, we can effectively reduce the occurrence of reflows and redraws, and improve the performance and user experience of web pages. However, it should be noted that different browsers may handle reflow and redrawing differently, so testing and optimization need to be carried out according to specific circumstances in actual development.

The above is the detailed content of How to reduce reflows and redraws. For more information, please follow other related articles on the PHP Chinese website!