how to retrieve ReadableStream data from res.body in JS

Question

I am fetching data from my backend using fetch function and it returns a readableStream as response's body. How can I extract the data in that readable stream? I've tries using res.json method, but it returns undefined. Here's my fetch call -

fetch('/playground',{
      method: 'POST',
    }).then(function(res){
      res.json()
    }).then(data => console.log(data))

it returns undefined in the console.

Here's the code from node.js server

router.route('/playground')
.post((req,res)=>{
    res.send({message: 'Hello from backend'})
})

I was expecting it to give me output as an object with key value pair as

{
  message: "Hello from backend"
}

but it returns undefined

------------UPDATE------------------------------ here's my entire router code, for a comment asked for it.

const express = require('express')
const router = express.Router()
const{scriptArray} = require('../Scripts/main')

router.route('/')
.get((req, res) =>{
    res.render('homepage')
})

router.route('/playground')
.get((req, res) =>{
    res.render('playground', {value: JSON.stringify(scriptArray)})
})
.post((req,res)=>{
    // console.log(req);
    res.send({message: 'Hello from backend'})
})

module.exports = {
    router,
}

Answer 1

You're not returning properly! Do this:

return res.json();