Javascript Express.js：以块形式发送响应

发布于05月06日

在Express.js上可以以数据块形式发送响应吗？我已经try 过(online demo):

const express = require('express');
const app = express();
const port = 3111;

const sleep = (ms) => {
  return new Promise((resolve) => setTimeout(resolve, ms));
};

app.get('/', async (req, res) => {
  res.setHeader('Content-Type', 'application/json');
  // flush to enable stream
  res.flushHeaders();
  res.write('[');
  for (let i = 1; i <= 1000; i++) {
    res.write(JSON.stringify(`data ${i}`));
    if (i + 1 <= 1000) {
      res.write(',');
    }
    await sleep(1);
  }
  res.write(']');
  res.end();
});

app.listen(port, () => {
  console.log(`App is live at http://localhost:${port}`);
});

但在Google Chrome和Postman上，只有在呼叫res.end()时才会显示响应

推荐答案

有一些考虑

您应该为application/stream+json等流添加正确的Content-Type
请记住，浏览器和一些HTTP客户端可能会缓冲响应(它们不会在块到达时显示，而是等到收到整个响应)，因此您可能需要考虑使用JavaScript来处理响应.
您不需要res.flushHeaders()，因为当您开始编写响应正文时，Express会自动处理它

import express from "express";
const app = express();

const sleep = (ms) => {
    return new Promise((resolve) => setTimeout(resolve, ms));
};

app.get('/stream', async (_req, res) => {
    res.setHeader('Content-Type', 'application/stream+json');

    res.write('[');
    for (let i = 1; i <= 1000; i++) {
        res.write(JSON.stringify(`data ${i}`));
        if (i < 1000) {
            res.write(",");
        }
        await sleep(1); // Simulates a delay
    }
    res.write(']');
    res.end();
});

const port = 3000;
app.listen(port, () => {
    console.log(`Server running on http://localhost:${port}`);
});