Improve page performance: To understand the performance bottlenecks of reflow and redraw, specific code examples are required
Overview:
When developing web applications, page performance is a Very important consideration. A high-performance web page not only provides a better experience for users, but also improves search engine rankings. To improve page performance, it is critical to understand the performance bottlenecks of reflow and redrawing.
Reflow and redraw refer to the process by which the browser calculates and renders the page based on CSS styles. Reflow refers to the process by which the browser completes all calculations and re-lays out the page, while redraw refers to the process by which the browser redraws the page according to the new style. Frequent occurrences of reflows and redraws will lead to reduced page performance, so we need to avoid this situation as much as possible.
Performance bottlenecks of reflow and redraw:
Code examples:
The following are some common code examples that easily lead to reflow and redrawing:
const element = document.getElementById('myElement'); for (let i = 0; i < 1000; i++) { element.style.width = '100px'; element.style.height = '100px'; // ...其他样式修改 }
Improvement method:
const element = document.getElementById('myElement'); element.classList.add('myClassName');
const element = document.getElementById('myElement'); for (let i = 0; i < 1000; i++) { element.innerHTML += '<div>' + i + '</div>'; }
Improvement method:
const element = document.getElementById('myElement'); const fragment = document.createDocumentFragment(); for (let i = 0; i < 1000; i++) { const div = document.createElement('div'); div.textContent = i; fragment.appendChild(div); } element.appendChild(fragment);
const element = document.getElementById('myElement'); const width = element.offsetWidth; const height = element.offsetHeight; // ...
Improvement method: Minimize the number of times to obtain element position information.
Conclusion:
In actual development, we need to optimize page performance, avoid triggering frequent reflows and redraws, and improve user experience and web page performance. By understanding the performance bottlenecks of reflow and redraw, we can optimize specific code fragments to reduce unnecessary calculation work and improve code running efficiency. Especially in scenarios involving a large number of DOM operations, proper use of the optimization methods in the code examples can significantly improve page performance.
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