JSFiddle - React, Tailwind, and code Playground

HTML

<div class="chat-input">
  <textarea placeholder="Write message..." ng-model="message" ng-keypress="keypress($event);"></textarea>
	<div class="chat-send"><img src="images/send.png" alt="" ng-click="sendMessage($event)"></div>
 </div>

JavaScript

//Клиент
$scope.sendMessage = function () {
	  var data = new Object();
    data.value    = $scope.message;
    data.username = username; // определено вне функции
    data.avatar   = avatar; // определено вне функции
    socket.emit("outgoingMessage", data);
    $scope.message = "";
  }
  
//Сервер
socket.on("outgoingMessage", (data) => {
  	this.io.sockets.emit("incomingMessage", data);
});