Im highly confused. The Duplex.from() method can take a object as src and creates fromt he object properties readable & writable a duplex stream:

converts readable and writable into Stream and then combines them into Duplex where the Duplex will write to the writable and read from the readable.

Why does my example not work?

const { PassThrough, Duplex } = require("stream");


const loopback = new PassThrough();


const duplex = Duplex.from({
    writable: loopback,
    readable: loopback
});


duplex.on("data", (chunk) => {
    console.log("Data on duplex", chunk)
});


duplex.write("Hello World");

My expected outcome is that the a duplex stream is created, and if so, that outputs the same i give as input. (Same as "echo", or plain passthrough stream)

Error message:

[nodemon] starting `node index.js`
internal/streams/from.js:32
    throw new ERR_INVALID_ARG_TYPE('iterable', ['Iterable'], iterable);
    ^

TypeError [ERR_INVALID_ARG_TYPE]: The "iterable" argument must be an instance of Iterable. Received an instance of Object
    at new NodeError (internal/errors.js:322:7)
    at from (internal/streams/from.js:32:11)
    at Function.Readable.from (internal/streams/readable.js:1368:10)
    at Object.<anonymous> (/home/marc/projects/test-stream/index.js:7:23)
    at Module._compile (internal/modules/cjs/loader.js:1085:14)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1114:10)
    at Module.load (internal/modules/cjs/loader.js:950:32)
    at Function.Module._load (internal/modules/cjs/loader.js:790:12)
    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:75:12)
    at internal/main/run_main_module.js:17:47 {
  code: 'ERR_INVALID_ARG_TYPE'
}

Can some one explain to my why i cant create a duplex stream from the a object?

Im a bit lost, since the docs say you can pass a object as argument, but the error message says "must be an instance of Iterable". As far as i know, a object is iterable. So whats the problem here?