Comparing optimization strategies for reflow and redraw: Exploration in pursuit of ultimate performance

Pursuit of ultimate performance: Comparison of optimization strategies for reflow and redraw

With the popularity of mobile devices and networks, users have also put forward higher requirements for the performance of applications. requirements. For front-end developers, optimizing the performance of web pages is very important. Reflow and repaint are two key factors that affect web page performance. This article will introduce the concepts of reflow and redraw, and compare their optimization strategies to pursue the ultimate performance.

1. The concept of reflow and redraw

Reflow means that the browser calculates the size and position of elements based on the DOM tree and CSS styles, determines their display on the page, and updates the layout at the same time information process. When the structure or style of the page changes, the browser needs to recalculate and draw the layout of the page. This process is called reflow.

Redrawing refers to the process in which the browser draws the style of an element to the screen based on new layout information. When an element's style changes, but does not affect its position and size on the page, the browser only needs to update the element's style without recalculating the element's layout.

Reflow and redraw are operations performed by the browser when rendering the page. They will consume computing resources and reduce the performance of the page.

2. Optimization strategies for reflow and redraw

1. Reduce the number of reflow and redraw

Avoid frequently modifying DOM elements and styles, which can reduce reflow and redraw. The number of draws. Multiple operations can be performed in one batch to update DOM elements and styles at once, reducing the workload of the rendering engine.

2. Use transform instead of top and left

When you need to change the position of an element, use the transform attribute instead of the top and left attributes to reduce reflow. Because the transform attribute only affects the rendering of the element and does not trigger reflow.

3. Use requestAnimationFrame

requestAnimationFrame is an API provided by the browser to optimize animation effects. Using requestAnimationFrame can execute code before the browser redraws next time, which can avoid unnecessary reflow and redrawing.

4. Use virtual DOM

Virtual DOM is a technology that represents the state of the page as a JavaScript object. By comparing the difference between the virtual DOM and the actual DOM, only updating the changed parts can reduce the number of reflows and redraws.

5. Use CSS animation

Using CSS animation can achieve smooth animation effects and reduce the number of reflows and redraws. CSS animations achieve animation effects by changing the style properties of elements without triggering layout updates.

3. Comparison of optimization strategies for reflow and redraw

Reflow and redraw are the two main operations of the browser when rendering the page. They both consume computing resources and reduce the performance of the page. The optimization strategy for reflow is mainly to reduce the number of reflows and avoid frequent modification of DOM elements and styles; while the optimization strategy for redrawing is mainly to reduce the number of redraws and avoid unnecessary style changes.

The performance consumption of reflow is higher than that of redraw, because reflow needs to recalculate the layout information of the page. Therefore, when optimizing performance, you should try to avoid reflow operations, use transform instead of top and left, and use virtual DOM and other technologies to reduce the number of reflows.

Although the performance consumption of redrawing is lower than that of reflow, it cannot be ignored. Therefore, when optimizing performance, it is also necessary to reduce unnecessary redraw operations and use CSS animation to reduce the number of redraws.

To sum up, reflow and redraw are key factors that affect web page performance. For applications that pursue ultimate performance, optimizing reflow and redraw operations is crucial. By reducing the number of reflows and redraws and using appropriate optimization strategies, the performance of web pages can be improved and provide a better user experience.

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