JavaScript WebSocket : EventTarget

constructor

WebSockets are a persistent connection to a server that allows sending and receiving data.

Spec

Constructors

new WebSocket(url : String) : WebSocket

Constructs a new WebSocket connection to url.

Example:

<script>
  // Connect to a WebSocket that echos back the messages it receives.
  var ws = new WebSocket('wss://echo.websocket.org/');
  ws.onopen = function(e) {
    console.log('WebSocket Opened. Sending "Hello"');
    ws.send('Hello');
  };

  ws.onmessage = function(e) {
    console.log('Received:', e.data);
  };
</script>

Run

Results:

new WebSocket(url : String, protocol : String) : WebSocket

Same as new WebSocket(url, [protocol]).

new WebSocket(url : String, protocols : Iterable<String>) : WebSocket

Instance Properties

binaryType : String

Set to either 'arraybuffer' or 'blob' to choose if the MessageEvent.data property will be an ArrayBuffer or a Blob for binary data received by the WebSocket.

Example:

<script>
  var testBinaryType = function(binaryType) {
    // Connect to a WebSocket that echos back the messages it receives.
    var ws = new WebSocket('wss://echo.websocket.org/');
    ws.binaryType = binaryType;
    ws.onopen = function(e) {
      ws.send(new Uint32Array([1, 2, 3]));
    };

    ws.onmessage = function(e) {
      // The type of the data will match the specified binaryType
      console.log(binaryType + ':', e.data);
    };
  };

  testBinaryType('arraybuffer');
  testBinaryType('blob');
</script>

Run

Results:

bufferedAmount : Number readonly

extensions : String readonly

protocol : String readonly

readyState : Number readonly

One of WebSocket.CONNECTING, WebSocket.OPEN, WebSocket.CLOSING, or WebSocket.CLOSED.

Example:

<button>Close</button>
<script>
  // Connect to a WebSocket that echos back the messages it receives.
  var ws = new WebSocket('wss://echo.websocket.org/');

  var readyStateNames = {
    [WebSocket.CONNECTING]: 'CONNECTING',
    [WebSocket.OPEN]: 'OPEN',
    [WebSocket.CLOSING]: 'CLOSING',
    [WebSocket.CLOSED]: 'CLOSED',
  };

  var logReadyState = function() {
    console.log(readyStateNames[ws.readyState]);
  };

  logReadyState();
  ws.onopen = logReadyState;
  ws.onclose = logReadyState;
  document.querySelector('button').onclick = function() {
    ws.close();
    logReadyState();
  };
</script>

Run

Results:

url : String readonly

The url passed to the WebSocket constructor.

Example:

<script>
  // Connect to a WebSocket that echos back the messages it receives.
  var ws = new WebSocket('wss://echo.websocket.org/');
  console.log(ws.url);
</script>

Run

Results:

Instance Methods

close([code : Number, [reason : String]]) : undefined

Closes the WebSocket connection.

send 4 variants

send(data : ArrayBuffer) : undefined

Sends data to the server.

send(data : ArrayBufferView) : undefined

Sends data to the server.

send(data : Blob) : undefined

Sends data to the server.

send(data : String) : undefined

Sends data to the server.

Instance Events

onclose / 'close' event

listener(event : CloseEvent) : undefined

onerror / 'error' event

listener(event : ErrorEvent) : undefined

onmessage / 'message' event

listener(event : MessageEvent) : undefined

onopen / 'open' event

listener(event : Event) : undefined

WebSocket Properties

CLOSED : Number readonly value = 3

The value of readyState after onclose fires.

CLOSING : Number readonly value = 2

The value of readyState after calling close() and before onclose fires.

CONNECTING : Number readonly value = 0

The value of readyState after constructing the WebSocket and before onopen fires.

OPEN : Number readonly value = 1

The value of readyState after onopen fires.

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