how to check monogdb database connection

Working with Node.js(monogdb, express and other modules) I'm wondering if there is a mongoose method for database connection, something like if I open a connection var db = mongoose.connect('mongo://localhost/members'); then I can db.on('close', function(){ /*do stuffs here*/}).

Basicly, the function below does the job of getting a user list from database and logging when database connection is closed.

So I need something in the if() to check database connection or whatever just unable to get data while its off and make a logging. I tried if(docs != null) it seems just off tho. Any advice would be much appreciated!

var logger = require('bunyan');

var log = new logger({
name: "loggings",
streams: [  
    {
        level: 'error',
        path: 'test.log',   
    }
],
serializers: {
    err: logger.stdSerializers.err,
}

});

function(req, res){
memberModel.find(function(err, docs){
    if (/*connection is closed*/) {
        res.render('users.jade', { members: docs });    
    }else{
            try {
                throw new DatabaseError ("Error!");
            } catch (err){
                log.warn({err: err}, "Check database connection!");
            }
        res.render('index.jade');
    };
});
};