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koa response image

koa.js

v1.x generator *function

v2.x Async/Await

koajs/examples

https://github.com/koajs/examples

https://github.com/koajs/examples/blob/master/stream-file/app.js

const Koa = require('koa');
const fs = require('fs');
const app = module.exports = new Koa();
const path = require('path');
const extname = path.extname;

// try GET /app.js

app.use(async function(ctx) {
  const fpath = path.join(__dirname, ctx.path);
  const fstat = await stat(fpath);

  if (fstat.isFile()) {
    ctx.type = extname(fpath);
    ctx.body = fs.createReadStream(fpath);
  }
});

if (!module.parent) app.listen(3000);

/**
 * thunkify stat
 */

function stat(file) {
  return new Promise(function(resolve, reject) {
    fs.stat(file, function(err, stat) {
      if (err) {
        reject(err);
      } else {
        resolve(stat);
      }
    });
  });
}

https://github.com/koajs/examples/tree/master/stream-server-side-events

https://github.com/koajs/examples/tree/master/templates/

demo

https://stackoverflow.com/questions/51571054/koa2-how-to-write-to-response-stream

'use strict';
const koa = require('koa');
const fs = require('fs');

const app = new koa();

const readable = require('stream').Readable
const s = new readable;

// response
app.use(ctx => {
    if (ctx.request.url === '/stream') {
        // stream data
        s.push('STREAM: Hello, World!');
        s.push(null); // indicates end of the stream
        ctx.body = s;
    } else if (ctx.request.url === '/file') {
        // stream file
        const src = fs.createReadStream('./big.file');
        ctx.response.set("content-type", "txt/html");
        ctx.body = src;
    } else {
        // normal KOA response
        ctx.body = 'BODY: Hello, World!' ;
    }
});

app.listen(8080);

---

OK

"use strict";

/**
 *
 * @author xgqfrms
 * @license MIT
 * @copyright xgqfrms
 * @created 2020-02-22
 * @modified
 *
 * @description
 * @augments
 * @example
 * @link
 *
 */

const log = console.log;

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

const fs = require('fs');
const path = require('path');
// const img = require('../poster.png');

// const readable = require('stream').Readable
// const s = new readable;

const img = fs.createReadStream('./poster.png');

// logger
app.use(async (ctx, next) => {
    await next();
    const rt = ctx.response.get('X-Response-Time');
    log(`${ctx.method} ${ctx.url} - ${rt}`);
});

// x-response-time
app.use(async (ctx, next) => {
    const start = Date.now();
    await next();
    const ms = Date.now() - start;
    ctx.set('X-Response-Time', `${ms}ms`);
});

// response
app.use(async ctx => {
    // node.js debugger
    // log(`ctx`, ctx);
    // log(`
ctx.request =
`, JSON.stringify(ctx.request, null, 4));
    // log(`
ctx.response 
`, JSON.stringify(ctx.response, null, 4));
    // ctx.body = 'Hello World';
    // ctx.body = img;
    ctx.response.set("content-type", "image/png");
    ctx.body = img;
    // response image
});

app.listen(3000);

refs

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