HTTP Cache-Control 与 ETag/Last-Modified 条件缓存实战

示例响应头：Cache-Control: public, max-age=3600, stale-while-revalidate=86400 ETag: "f1a2-3c4d" Last-Modified: Wed, 26 Nov 2025 10:00:00 GMT 条件请求（客户端）：GET /app.css HTTP/1.1 If-None-Match: "f1a2-3c4d" If-Modified-Since: Wed, 26 Nov 2025 10:00:00 GMT 服务端返回未变更：HTTP/1.1 304 Not Modified Cache-Control: public, max-age=3600, stale-while-revalidate=86400 ETag: "f1a2-3c4d" Node.js 示例：import express from 'express' const app = express() app.get('/api/data', (req, res) => { const etag = '"data-v1"' res.set('Cache-Control', 'public, max-age=300, stale-while-revalidate=86400') res.set('ETag', etag) const inm = req.headers['if-none-match'] if (inm === etag) return res.status(304).end() res.json({ ok: true, ts: Date.now() }) }) app.listen(3000)