React-Native Websocket Event data property is missing - ios

Question

I am trying to connect to the Watson TTS API over a Websocket connection in React-Native. The connection is established and I can send a message to the server, however the data that I get back from the server somehow always is empty.
It seems as if the event.data property is completely missing. If I log it to the console in react-native I get 'undefined' as a result. If i use the same code in the browser everything works perfectly.
I am using react-native 0.33 and here's my code:
function connectTTS(token) {
var voice = "de-DE_BirgitVoice";
var format = 'audio/basic';
var token = token;
var wsURI = "wss://stream.watsonplatform.net/text-to-speech/api/v1/synthesize?voice=" + voice + "&watson-token=" + token;
function onOpen(evt) {
var message = {
text: "Hello world.",
accept: format
};
// note: the Text to Speech service currently only accepts a single message per WebSocket connection
websocket.send(JSON.stringify(message));
}
var audioParts = [];
var finalAudio;
function onMessage(evt) {
console.log(evt.data);
if (typeof evt.data === 'string') {
console.log('Received string message: ', evt.data)
} else {
console.log('Received ' + evt.data.size + ' binary bytes', evt.data.type);
audioParts.push(evt.data);
}
}
function onClose(evt) {
console.log('WebSocket closed', evt.code, evt.reason);
console.log(audioParts);
console.log(format);
finalAudio = new Blob(audioParts, {type: format});
console.log('final audio: ', finalAudio);
}
function onError(evt) {
console.log('WebSocket error', evt);
}
var websocket = new WebSocket(wsURI);
websocket.onopen = onOpen;
websocket.onclose = onClose;
websocket.onmessage = onMessage;
websocket.onerror = onError;
}
It would be great if somebody with more react-native / websocket experience could help me find the solution. Thanks.

Answer 1

In react-native up to 0.53 (latest version at the moment), react-native WebSocket event processing relies on event-target-shim 1.1.1 lib which wraps an event and does not include data to the wrapped event, so in order to get WebSocket event data you may use one of two approaches:
Get data from __proto__;
Rewrite event-target-shim 1.1.1;
The first approach:
use <your event>.__proto__.__proto__.data
The second approach:
fork event-target-shim and reset to event-target-shim 1.1.1;
fork react-native;
Add the code listed below to the event-target-shim/lib/event-wrapper.js;
rewrite react-native package.json to use forked version of the event-target-shim;
rewrite package.json of your project;
Code to add in exports.createEventWrapper after var propertyDefinition = {...}:
if (event.type === "message"){
propertyDefinition.data = {value: event.data, enumerable: true};
}