深入探索 Node.js 核心机制与实践智慧

1const NS_PER_SEC = 1e9
2function measure() {
3    const start = process.hrtime.bigint()
4    // 被测操作
5    const diff = process.hrtime.bigint() - start
6    return Number(diff / NS_PER_SEC) + 's ' + Number(diff % NS_PER_SEC) + 'ns'
7}

1const activeResources = new Map()
2
3async_hooks.createHook({
4    init: (asyncId, type) => activeResources.set(asyncId, { type, stack: new Error().stack }),
5    destroy: (asyncId) => activeResources.delete(asyncId)
6}).enable()
7
8setInterval(() => {
9    console.log(`Active async resources: ${activeResources.size}`)
10}, 1000)

1import { AsyncLocalStorage } from 'async_hooks'
2
3type RequestContext = {
4    requestId: string
5    user?: { id: string }
6}
7
8const contextStorage = new AsyncLocalStorage<RequestContext>()
9
10app.use((req, res, next) => {
11    const store = { requestId: uuidv4() }
12    contextStorage.run(store, () => next())
13})
14
15app.get('/data', async () => {
16    const dbQuery = async () => {
17        // 深层调用仍可获取上下文
18        const { requestId } = contextStorage.getStore()!
19        return await fetchData(requestId)
20    }
21    return await dbQuery()
22})

1import { promises as fs } from 'fs'
2
3async function safeWrite(path: string, content: Buffer) {
4    await fs.mkdir(dirname(path), { recursive: true })
5    await fs.writeFile(path, content, { flag: 'wx' }) // 独占写入
6}

1# 启用无缓冲输出
2node server.js | tee -a app.log

1const getGlobal = () => {
2    if (typeof globalThis !== 'undefined') return globalThis
3    if (typeof self !== 'undefined') return self
4    if (typeof window !== 'undefined') return window
5    return Function('return this')()
6}

1ArrayBuffer (16 bytes)
2+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
3| 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 |11 |12 |13 |14 |15 |
4+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
5
6Uint8Array 视图
7[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
8
9DataView 访问示例
10getUint32(0, true) -> 小端序读取前4字节

1// Buffer 与 ArrayBuffer 互转
2const bufferToArrayBuffer = (buf: Buffer) => buf.buffer.slice(buf.byteOffset, buf.byteOffset + buf.byteLength)
3
4// Stream 处理优化
5function processStream(stream: Readable) {
6    const decoder = new TextDecoder()
7    let buffer = new Uint8Array()
8    
9    stream.on('data', chunk => {
10        buffer = concatUint8Arrays(buffer, chunk)
11        while(buffer.length >= 4) {
12            const length = new DataView(buffer.buffer).getUint32(0)
13            if(buffer.length < 4 + length) break
14            
15            const message = decoder.decode(buffer.subarray(4, 4 + length))
16            buffer = buffer.slice(4 + length)
17            handleMessage(message)
18        }
19    })
20}