var msg =
{
  "jsonrpc" : "2.0",
  "id" : 7617,
  "method" : "public/get_instruments",
  "params" : {
    "currency" : "BTC",
    "kind" : "option",
    "expired" : false
  }
};
var ws = new WebSocket('wss://test.deribit.com/ws/api/v2');
ws.onmessage = function (e) {
    // do something with the response...
    console.log('received from server : ', e.data);
};
ws.onopen = function () {
    ws.send(JSON.stringify(msg));
};