How to use ES6 import in worker thread in Node.js?

Question

How to use ES6 import in worker thread?

I'm trying to utilize ES6 import syntax in a worker thread in a Node.js environment. However, I'm encountering issues with the import statement. Here's a simplified version of my code: app.js

import express from 'express'
import bodyParser from 'body-parser'
import os from 'os'
import { Worker } from 'worker_threads'

const app = express()
const router = express.Router()
app.use(bodyParser.urlencoded({ extended: false }))
app.use(bodyParser.json())
app.use('/api', router)
router.get('/worker-thread', (req, res) => {
  const worker = new Worker('./worker_thread/index.js')
  worker.on('message', (j) => {
    return res.status(200).json({ value: j, message: 'running successfully' })
  })
})
app.listen(4000, () => {
  console.log('PORT RUNNING ON 4000')
})

worker_thread.js

import { parentPort } from 'worker_threads';

let j = 0;

for (let i = 0; i < 5000000000; i++) {
  j++;
}

parentPort.postMessage(j);

Running this code results in a SyntaxError: Cannot use import statement outside a module. I want to leverage ES6 features within the worker thread. What's the correct way to achieve this without transpiling the code?

Run your main script with the --experimental-worker flag: like this: node --experimental-worker your_main_script.js . but also you didn't share your full main script because you can create and run the worker thread: — Adesoji Alu
– Adesoji Alu, Commented Nov 16, 2023 at 11:24
i update the code now please check it & i also tried the solution that you provided.it didn't work as well — Amitprj
– Amitprj, Commented Nov 16, 2023 at 12:25
You have 2 choices. Either name all your files .mjs instead of .js or add "type": "module" in package.json — slebetman
– slebetman, Commented Nov 17, 2023 at 3:28

LmanTW · Accepted Answer · 2023-11-17 02:32:32Z

2

I tried to run your code, it run successfully with no problem, the url return {"value":1000,"message":"running successfully"} (I change the loop for testing)

File Structure:

app.js

worker_thread

｜child_thread.js

package.json

package.json:

{
  "type": "module",
  "dependencies": {
    "body-parser": "^1.20.2",
    "express": "^4.18.2"
  }
}

I'm guessing that maybe in your worker_thread/child_thread.js node.js couldn't find your package.json to know it's using ES6, please tell me if I did something wrong when trying to reproduce this error :D

answered Nov 17, 2023 at 2:32

LmanTW

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