Decrypt the working principle of CSS reflow and redraw
Introduction:
In the process of web development, we often hear about CSS reflow (reflow) and redraw. The two concepts of repaint. Understanding how they work is crucial to optimizing web page performance and improving user experience. This article will delve into how CSS reflow and repaint work, and provide specific code examples to help readers better understand these two concepts.
1. How CSS reflow works
1.1 What is CSS reflow
CSS reflow refers to the process in which the browser recalculates the position and size of elements and updates the page layout. When the layout properties of an element on the page change, CSS reflow is triggered.
1.2 Trigger conditions for CSS reflow
The following situations will trigger CSS reflow:
1.3 The process of CSS reflow
The process of CSS reflow is as follows:
1.4 How to avoid unnecessary CSS reflow
In order to improve web page performance, we can avoid some unnecessary CSS reflow. The following are several common optimization methods:
2. How CSS redrawing works
2.1 What is CSS redrawing
CSS redrawing refers to the process in which the browser redraws the page according to changes in style. When the style attribute of an element on the page changes, a CSS redraw is triggered.
2.2 Trigger conditions for CSS redrawing
The following situations will trigger CSS redrawing:
2.3 The process of CSS redrawing
The process of CSS redrawing is as follows:
2.4 How to avoid unnecessary CSS redrawing
In order to improve web page performance, we can avoid some unnecessary CSS redrawing. The following are several common optimization methods:
3. Code Example
The following is a simple code example that demonstrates how to avoid unnecessary CSS reflow and redrawing.
<!DOCTYPE html> <html> <head> <style> .box { width: 100px; height: 100px; background-color: red; transition: width 1s; } </style> </head> <body> <div class="box"></div> <button onclick="changeWidth()">改变宽度</button> <script> function changeWidth() { var box = document.querySelector('.box'); // 触发一次CSS回流和重绘 box.style.width = '200px'; } </script> </body> </html>
In the above code, when the button is clicked to change the width of the box, due to the use of the transition
attribute, the browser will use CSS animation to transition the width change, thereby triggering CSS only once Reflow and redraw, improved performance.
Conclusion:
This article decrypts the working principles of CSS reflow and redraw in depth and provides specific code examples. By understanding how these two concepts work, we can optimize web page performance and improve user experience. I hope readers can use this knowledge to better develop high-performance web pages.
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