Simulate callback handling for OpenRPC websockets

websockettransport_notify.js

var conn = this.socket.connection;
conn.send(
    JSON.stringify({
        jsonrpc: '2.0',
        method: method,
        params: params,
    })
);
if (cb) {
    //The notify promise does not resolve on all browsers
    //so we resort to polling
    setTimeout(function () {
        if (conn.bufferedAmount < 1) cb();
        else
            var a = setInterval(function () {
                if (conn.bufferedAmount < 1) {
                    clearInterval(a);
                    cb();
                }
            }, 25);
    }, 500);
}