Optimize front-end engineering: improve page performance and user satisfaction, and effectively solve page redrawing and reflow issues

Front-end engineering optimization: To deal with page redrawing and reflow, improve page performance and user satisfaction, specific code examples are needed

With the rapid development of Internet technology, more and more More and more companies and individuals are beginning to realize the importance of web page performance. Optimizing front-end engineering can not only improve the loading speed of the website, but also increase user satisfaction and improve user experience. In front-end engineering optimization, handling page redrawing and reflow is a very critical issue.

Page redrawing and reflow refers to the process of the browser re-rendering the web page. When the user performs an operation or the web page elements change, the browser needs to recalculate the web page layout and redraw the changed parts on the screen. This process is very performance-intensive and can cause page freezes and slow loading speeds. Therefore, we need to adopt some optimization strategies to reduce page redraws and reflows, and improve page performance and user satisfaction.

1. Avoid frequent manipulation of styles

When writing front-end code, we should try to avoid frequent manipulation of styles. Because every change in style will trigger a redraw and reflow of the page. If you need to modify multiple styles, you can consider using CSS classes to modify the styles of multiple elements at once. This can reduce the number of redraws and reflows and improve page performance.

<!-- 不推荐 -->
<div style="color:red;font-size:16px;">Hello World!</div>

<!-- 推荐 -->
<style>
    .red-text {
        color: red;
        font-size: 16px;
    }
</style>

<div class="red-text">Hello World!</div>

2. Using document fragments

Document fragment (DocumentFragment) is a special DOM node that can be used to insert multiple sub-elements into the DOM structure at one time. Using document fragments can reduce the number of DOM operations, thereby reducing page redraws and reflows.

// 创建文档片段
var fragment = document.createDocumentFragment();

// 循环创建多个元素节点，并添加到文档片段中
for (var i = 0; i < 1000; i++) {
    var element = document.createElement('div');
    element.textContent = 'Hello World!';
    fragment.appendChild(element);
}

// 将文档片段一次性插入到 DOM 结构中
document.body.appendChild(fragment);

3. Use flag bits to operate DOM

Sometimes we need to modify the DOM multiple times, but this will lead to multiple page redraws and reflows. In order to reduce the occurrence of this situation, we can use flag bits to save modifications, and finally update the DOM uniformly. This can reduce the number of page redraws and reflows and improve page performance.

// 设置标志位，表示样式需要更新
var needUpdate = false;

// 修改样式时，仅设置标志位，不进行实际操作
function updateStyle() {
    needUpdate = true;
}

// 在合适的时机，检查标志位，并更新 DOM
function render() {
    if (needUpdate) {
        document.getElementById('element').style.color = 'red';
        // ... 其他修改样式的操作
        needUpdate = false;
    }
}

Through the above example code, we can see that optimization of page redrawing and reflow can be achieved by reducing the number of style operations, using document fragments and flag bits to operate DOM, etc. Reasonable optimization of these aspects can significantly improve page performance, increase user satisfaction and improve user experience. For front-end engineers, it is very important to master these optimization skills. I believe that through continuous learning and practice, we can create more efficient and faster web applications.

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