Will the redesign cause reflux?

Will redrawing cause reflow? Specific code examples are needed

Reflow (Reflow) refers to the browser loading and rendering the page according to the size and position of the element. The process of calculating and determining its exact position on the page. Repaint refers to the process in which the browser redraws the appearance of the element when the style of the page element changes. In front-end development, understanding the mechanics of reflow and redraw is crucial to optimizing page performance.

The overhead of reflow and redraw is very high, so we need to minimize the number of times they are triggered to improve the rendering performance of the page. When page elements change, the browser will perform reflow and redraw operations, and the triggering of these operations is conditional. Let's take a look at some specific code examples to see which operations trigger reflow and redraw.

1. Modify the size of the element

// 错误示例
// 修改元素的宽度和高度属性
element.style.width = '200px';
element.style.height = '300px';

// 正确示例
// 使用 CSS 类名来修改元素的样式
element.classList.add('big');

Changing the size of the element directly by modifying the style attribute will cause reflow and redrawing. If you use CSS class names to modify the size of the element, it will only cause redrawing, avoiding expensive reflow operations.

2. Modify the position of the element

// 错误示例
// 修改元素的 left 和 top 属性
element.style.left = '50px';
element.style.top = '100px';

// 正确示例
// 使用 transform 来改变元素的位置
element.style.transform = 'translate(50px, 100px)';

Directly modifying the position attribute of the element will cause reflow and redrawing. Using the transform attribute to change the position of an element will only cause redrawing, not reflow.

3. Getting the size or position attributes of certain elements

// 错误示例
// 在操作之前多次获取元素的尺寸或位置
const width = element.offsetWidth;
const height = element.offsetHeight;

// 正确示例
// 在一次性获取所有元素尺寸或位置属性
const rect = element.getBoundingClientRect();
const width = rect.width;
const height = rect.height;

Getting the size or position attributes of certain elements multiple times will also cause a reflow operation. You should try to avoid multiple retrievals and get all the required properties at once.

In summary, avoid directly modifying the size and position attributes of elements, and try to use CSS class names and transform attributes to change the style and position of elements. In addition, if you need to obtain the size or position attributes of an element, you should obtain them once to avoid repeated accesses. This can reduce the number of reflows and redraws and improve the rendering performance of the page.

Of course, the above are just some common examples of operations that trigger reflow and redraw. The specific situation needs to be analyzed and optimized based on the actual project. During the development process, we should always pay attention to the performance bottlenecks of the page, reduce unnecessary reflows and redraws, improve user experience, and improve website performance.

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