Unable to access Array inside JSON object

For the life of me, I can not figure out why this is not working.

I am opening a websocket connection using WS v8+

I receive a message and parse it to JSON.

ws.on('message', function message(data) {
  var message = data.toString()
  console.log(message)
});

Now the output is as expected:

{"method": "state.update", "params": [{"BTCUSDT": {"last": "27427.41"}}], "id": null}

I can read the message.method and message.params as expected. The problem is accessing the array inside "params":

ws.on('message', function message(data) {
  var message = data.toString()
  console.log(data.params[0]) // FAILS
});

ws.on('message', function message(data) {
  var message = data.toString()
  console.log(data.params)
  // OUTPUT: [{"BTCUSDT": {"last": "27427.41"}}]
});

For the life of me I can't figure out why it is failing to see the params as an array with any length for this very simple task.

UPDATE:

With the WS library, the need to use toString() from the Buffer was there. With WS 7 this was not needed.

Also the params field is not showing up as an array which explains why length and other indexes aren't working but very confused as why it isn't being read as an array with the output I am seeing.

ws.on('message', function message(data) {
    var message = data.toString()
    var output = JSON.parse(message)
    console.log( Array.isArray(output.params) )    // RETURNS FALSE   
 }); 

Assuming you're using this ws library, it appears you're assuming the data is in JSON format, but I can't find any documentation to support that assumption.

Try calling JSON.parse(data) before iterating your object.

ws.on('message', function message(data) {
  var json = JSON.parse(data) // <----- HERE
  console.log(json.params[0])
});