Midjourney API in Node.js

// Node.js 18+ (built-in fetch). Run: USERAPI_KEY=... node client.mjs
import { writeFile } from 'node:fs/promises';

const API_BASE = 'https://api.userapi.ai/midjourney/v2';
const HEADERS = {
  'api-key': process.env.USERAPI_KEY,
  'Content-Type': 'application/json',
};

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

// Start a task and return its hash.
async function post(method, payload) {
  const res = await fetch(`${API_BASE}/${method}`, {
    method: 'POST',
    headers: HEADERS,
    body: JSON.stringify(payload),
  });
  if (!res.ok) throw new Error(`${method}: HTTP ${res.status} ${await res.text()}`);
  const { hash } = await res.json();
  return hash;
}

// Poll the status endpoint until the task is done or failed.
async function wait(hash, { interval = 5000, timeout = 600000 } = {}) {
  const deadline = Date.now() + timeout;
  while (Date.now() < deadline) {
    const res = await fetch(`${API_BASE}/status?hash=${hash}`, { headers: HEADERS });
    if (!res.ok) throw new Error(`status: HTTP ${res.status}`);
    const task = await res.json();
    if (task.status === 'done') return task;
    if (task.status === 'error') {
      throw new Error(`task failed: ${task.status_reason} ${JSON.stringify(task.prefilter_result ?? [])}`);
    }
    console.log(task.status, `${task.progress ?? 0}%`);
    await sleep(interval);
  }
  throw new Error(`timeout waiting for ${hash}`);
}

// 1. Generate a grid of four images
const grid = await wait(await post('imagine', { prompt: 'a red fox in a snowy forest, cinematic light --ar 3:2' }));
console.log('grid:', grid.result.url);

// 2. Upscale the second image of the grid
const upscaled = await wait(await post('upscale', { hash: grid.hash, choice: 2 }));

// 3. Save it: Discord CDN links are not permanent storage
const image = await fetch(upscaled.result.url);
await writeFile('fox.png', Buffer.from(await image.arrayBuffer()));
console.log('saved fox.png');

const hash = await post('imagine', {
  prompt: 'isometric cozy coffee shop, soft pastel colors',
  webhook_url: 'https://your-server.com/midjourney/webhook',
  webhook_type: 'result', // or 'progress' for every progress update
});

// npm install express
import express from 'express';

const app = express();
app.use(express.json({ limit: '1mb' }));

app.post('/midjourney/webhook', (req, res) => {
  const task = req.body;
  if (task.status === 'done') {
    console.log(task.type, task.hash, task.result.url);
  } else if (task.status === 'error') {
    console.log('failed:', task.hash, task.status_reason);
  } else {
    console.log(task.hash, task.status, task.progress);
  }
  res.sendStatus(200);
});

app.listen(3000);

const prompts = ['a lighthouse at dawn', 'a lighthouse at noon', 'a lighthouse at night'];

// Without account_hash, tasks are rotated across the Discord accounts linked to your API key.
const results = await Promise.allSettled(prompts.map(async (prompt) => wait(await post('imagine', { prompt }))));

results.forEach((r, i) => {
  console.log(prompts[i], '->', r.status === 'fulfilled' ? r.value.result.url : r.reason.message);
});