Resource Timing API：资源加载性能采集与分析

概述Resource Timing 提供从重定向到下载完成的各阶段时间戳，适合分析 DNS、TCP/TLS、TTFB 与传输耗时，定位瓶颈与优化方向。用法/示例new PerformanceObserver(list => { for (const e of list.getEntries()) { const d = e.responseEnd - e.startTime } }).observe({ type: 'resource', buffered: true }) const entries = performance.getEntriesByType('resource') for (const e of entries) { const dns = e.domainLookupEnd - e.domainLookupStart const tcp = e.connectEnd - e.connectStart const tls = e.secureConnectionStart > 0 ? e.connectEnd - e.secureConnectionStart : 0 const ttfb = e.responseStart - e.requestStart const transfer = e.responseEnd - e.responseStart } 工程建议将关键资源的时序与路径关联分析，结合缓存与预连接策略优化。过滤跨源与隐私受限条目，遵守安全与隐私政策。与后端 Server-Timing 合并做端到端观测与归因。参考与验证MDN：Resource Timing — https://developer.mozilla.org/docs/Web/API/Resource_Timing_APIW3C：Resource Timing — https://www.w3.org/TR/resource-timing-2/