the following code works:

Experimenters = function(db)
{
    Object.apply(this, arguments);
    this.db = db;
};
util.inherits(Experimenters, Object);


Experimenters.prototype.getAll = function(req, res)
{    
    return this.db.Experimenter.getAllExperimentersWithExperiments()
    .then(function(exptrs) {
        res.json(200, exptrs);
    })
    .catch(function(error) {
        res.json(500, error);
    });
};

however the code for each of my request handlers is pretty much all the same, so I thought I'd reduce duplicate code by creating a generic request handler:

Experimenters.prototype.handleRequest = function(promise, res)
{
    return promise
    .then(function(success){
        res.json(200, success);
    })
    .catch(function(error) {
        if (error instanceof dbErrors.NotFoundError) {
            res.json(404, error);
        } else if ((error instanceof dbErrors.ValidationError) ||
                   (error instanceof dbErrors.UniqueConstraintError)) {
            res.json(422, error);
        } else {
            // unknown error
            console.error(error);
            res.json(500, error);
        }
    });
};

And modify my request handlers like this:

Experimenters.prototype.getAll = function(req, res)
{
    this.handleRequest(
        this.db.Experimenter.getAllExperimentersWithExperiments(),
        res);
};

But I'm getting:

TypeError: Object #<Object> has no method 'handleRequest' 

the code is called via my routes/index.js

// edited for brevity
var Experimenters = require("../controllers/experimenters");

module.exports.initialize = function(app)
{
    var exptrs = new Experimenters(app.db);

    app.get("/api/experimenters", exptrs.getAll);
};

which is called from my app.js:

 //edited for brevity
 var config = require(path.join(__dirname, "..", "config")),
     createDB = require(path.join(__dirname, "models")),
     routes = require(path.join(__dirname, "routes"));

 var db = createDB(config);
 app.set("db", db);
 // edited for brevity
 routes.initialize(app);