Node.js 常见问题漫谈

const Koa = require("koa");
const app = new Koa();

const requestMap = new Map();

// middleware
app.use((ctx) => {
  requestMap.set(ctx.req, ctx.uid);
});

// middleware
app.use((ctx) => {
  ctx.redis = new Redis();
});

// middleware
app.use((ctx) => {
  ctx.logger = fs.createWriteStream(`/tmp/foo-${Date.now()}.log`);
});

const dxfText = await this.dxfService.getDXFContent(
  projectId,
  projectOwnerId,
  modeCateName,
  scienceName,
  knifeData,
  remark,
  removeLogo
);
const yunFile = await this.qiniu.putFileFromBuffer(
  `export/dxf/temp/${uuidv4()}.dxf`,
  Buffer.from(dxfText, "utf8")
);

const r = fs.createReadStream("file.txt");
const z = zlib.createGunzip();
const w = fs.createWriteStream("file.txt.gz");

r.pipe(z)
  .pipe(w)
  .on((err) => {
    console.error("Pipeline failed", err);
  });

pipeline(
  fs.createReadStream("archive.tar"),
  zlib.createGzip(),
  fs.createWriteStream("archive.tar.gz"),
  (err) => {
    if (err) {
      console.error("Pipeline failed", err);
    } else {
      console.log("Pipeline succeeded");
    }
  }
);

setInterval(async () => {
  try {
    await fetch("https://127.0.0.1:8080/health_check");
  } catch (e) {
    console.error(e);
  }
}, 3000);

const timer = setTimeout(async () => {
  try {
    await fetch("https://127.0.0.1:8080/health_check");
  } catch (e) {
    console.error(e);
  } finally {
    timer.refresh();
  }
}, 3000);

// bad
await fetch("https://127.0.0.1:8080/third_party");

// good
await fetch("https://127.0.0.1:8080/third_party", { timeout: 5000 });

function loadFile(name) {
  const jsonFile = `/tmp/${name}.json`;
  return require(jsonFile);
}

loadFile("foo");

const EventEmitter = require("events");

class MyEventEmitter extends EventEmitter {
  retry() {
    this.on("event", () => {
      console.log("an event occurred");
    });
    return this;
  }
}

const e = new MyEventEmitter();
e.retry();