WebSocketStream API came into play to make things easier with WebSocket API, which has the below limitations:

• Ergonomics isn’t great
• The important feature of backpressure is missing
• The onmessage event will keep firing until the page becomes completely unresponsive
• To find out when it is safe to start sending messages again, it is necessary to poll bufferedAmount

Goals of WebSocketStream API

• Provide a WebSocket API that supports backpressure
• Provide a modern, ergonomic, easy-to-use WebSocket API
• Allow for future extension

From the explainer.

Sample Code

(async () => {
  const wss = new WebSocketStream("wss://echo.websocket.org/");
  const { readable, writable } = await wss.connection;
  const reader = readable.getReader();
  
  await writable.getWriter().write("echo");
  const { value, done } = await reader.read();
  console.log(value, done);
})();