getOnline (args, util) {
        const status = window.navigator.onLine;
        if (typeof status === 'boolean') {
            return status;
        }
        // an empty string will evaluate as false in a Boolean context,
        // but it allows distinguishing between "false" and "unknown" if needed
        return '';
    }
    getUsername (args, util) {
        return util.ioQuery('userData', 'getUsername');
    }

        <block id="online" type="sensing_online" />
        <block type="sensing_username"/>
    sensing_online: {
        defaultMessage: 'online',
        description: 'Label for the online status monitor when shown on the stage',
        id: 'gui.opcodeLabels.online'
    },
    sensing_username: {
        defaultMessage: 'username',
        description: 'Label for the username monitor when shown on the stage',
        id: 'gui.opcodeLabels.username'
    },

        this._translator = message => message.defaultMessage;
        this._opcodeMap.sensing_online.labelFn = () => this._translator(messages.sensing_online);
        this._opcodeMap.sensing_username.labelFn = () => this._translator(messages.sensing_username);

Blockly.Msg.SENSING_ONLINE = 'online?'
Blockly.Msg.SENSING_USERNAME = 'username'