title: Does JavaScript WebSocket.send method block?
body: <p>If I'm sending a large <code>Blob</code> or <code>ArrayBuffer</code> over a JavaScript <code>WebSocket</code> via its <code>send</code> method... does the <code>send</code> method call block until the data is sent, or does it make a copy of the data to send asynchronously so the call can return immediately?</p>
  
  <p>A related (unanswered) question is, from how I interpret it, whether a rapid series of sends will cause onmessage events to be delayed, as someone seems to have described happening in Mobile Safari: <a href="https://stackoverflow.com/questions/17219963/apparent-blocking-behaviour-in-javascript-websocket-on-mobile-safari">Apparent blocking behaviour in JavaScript websocket on mobile Safari</a> </p>