My .mongorc.js file

.mongorc.js

(function () {
rcversion = '1.0';

load('underscore.min.js')

// NOTES
// Basics, wrap the whole thing in a function
// Set a version for sanity's sake
// Load underscore, a must in any javascript environment

(function () {
    var cmdCount = 0;
    var isMaster = db.isMaster();

    if (isMaster.setName) {
        prompt = function () {
            return isMaster.setName +  '(' + (isMaster.ismaster() ? 'pri' : 'sec' ) + '):' + db + '-' + (cmdCount++) + ' > ';
        };
    } else {
        prompt = function () {
            return db + '-' + (cmdCount++) + ' > ';
        };
    }
})()

// NOTES
// Setup the prompt
// This prompt tells us if we are on a replica set, and if we are on the primary
// It also shows the current database and the current command count

var login = function (dbname, username) {
    // Or load('auth_tokens.js')
    var tokens = {
        'admin-username': 'admin-password',
        'readonly-username': 'foo-readonly-password',
        'readwrite-username': 'foo-readwrite-password'
    };
        // Only login on the correct database.
    if (dbname !== db) {
        db.auth(username, tokens[username]);
    }
};

auth = {
    admin: _.bind(login, 'admin', 'admin-username'),
    ro: _.bind(login, 'foo', 'readonly-username'),
    rw: _.bind(login, 'foo', 'readwrite-username')
};

// NOTES
// Setup authentication helpers.
// Add in your own authentication schemes and tokens. (you can also load these from another file)
// This provides some nice functions like `auth.rw()` to authenticate read-write

_.mixin({
    // A deep getter
    get: function (obj, key) {
        return _.reduce(key.split('.'), function (o, k) {
            return o && o[k];
        }, obj);
    },

    // Get a random integer
    randint: function (n) {
        return Math.floor(Math.random() * (n || 2));
    },

    // Get a random choice
    randchoice: function (seq) {
        return seq[_.randint(seq.length)];
    },

    // Get the current timestamp
    now: function () {
        return (new Date()).getTime() / 1000;
    },

    // Create an object id based on a timestamp
    oid: function(timestamp) {
        if (!timestamp) {
            return new ObjectId();
        }

        // Convert string date to Date object (otherwise assume timestamp is a date)
        if ( ! timestamp instanceof Date ) {
            timestamp = new Date( timestamp );
        }

        // Convert date object to hex seconds since Unix epoch
        var hexSeconds = Math.floor( timestamp / 1000 ).toString( 16 );

        // Create an ObjectId with that hex timestamp
        return ObjectId( hexSeconds + "0000000000000000" );
    },

    // Aggregate sequence into prefix sequences
    aggregate: function (seq) {
        return _.reduce(seq, function (memo, nxt) {
            var agg = memo[0], cur = memo[1].concat(nxt);
            return [agg.concat([cur]), cur];
        }, [[], []])[0];
    },

    // Aggregate and join a sequence of strings
    aggjoin: function (seq, sep) {
        return _.map(_.aggregate(seq), function (agg) {
            return agg.join(sep);
        });
    },

    // Sum a sequence of numbers
    sum: function (seq) {
        return _.reduce(seq, function (a, b) { return a + b; }, 0);
    }
});

// NOTES
// Various useful helper functions. I just stick them on the underscore object to make using them
// easer. I don't have to remember multiple helper objects. Especially helpful is _.oid, which
// is oddly missing from the shell functions.

// Walks a recursive object (`node`), testing them with tester and making callbacks when tester returns true.
// The only option is `depth`: defaults to 20 but can be set arbitrarily (up to shell limit) to control recursion.
var walker = function (node, tester, callback, opts) {
    depth = (opts || {}).depth || 20;
    var walk;
    walk = function (branch, n) {
        n = n || 0;
        if (n > depth) return null;

        if (tester(branch)) {
            callback(branch);
        }

        if (_.isObject(branch) || _.isArray(branch)) {
            _.each(branch, function (subbranch) {
                walk(subbranch, n + 1);
            });
        }
    }
    return walk(node);
};

// NOTES
// This is a base function for walking a tree structure to find things.
// Mongo is based off of javascript objects, which are so easy to nest.
// We have some arbitrarily nested structures in our database, and parsing
// them in the shell is tedious at best. We'll start with this and build up
// some useful functions for dealing with arbitrarily nested data.

// Take a selector and create a testor for the walker function
// The goal is to create a tester that will find objects with certain
// key/value pairs.
// Selectors can be strings, objects, or arrays.
// Objects and arrays just create AND filters trying to match part of objects
// String filters can be 'FIELD:' (to search for having the field 'FIELD')
// or 'FIELD:VALUE' to search for string equality.
var kv_typetest = function (selector) {
    var expect = {}, match = {}, tests = [];
    if (_.isString(selector)) {
        _.each(selector.split(' '), function (sel) {
            var kvsplit = sel.split(':');
            if (kvsplit.length === 1) {
                expect[kvsplit[1]] = true;
            } else if (kvsplit.length === 2) {
                match[kvsplit[0]] = kvsplit[1];
            }
        });
    } else if (_.isObject(selector)) {
        expect = selector;
    } else if (_.isArray(selector)) {
        tests = _.map(selector, kv_typetest);
    } else {
        throw new Error("Expected string or object for selector");
    }

    return function (branch) {
        return _.every(expect, function (value, key) {
            if (value instanceof RegExp) {
                return value.test(_.get(branch, key));
            } else {
                return _.isEqual(_.clone(_.get(branch, key)), value);
            }
        }) && _.every(match, function (_value, key) {
            return branch.hasOwnProperty(key);
        }) && _.every(tests, function (t) {
            return t();
        });
    };
};

// NOTES
// Here, I start to build a tester function for the walker base function
// We start to introduce something of the ease of jquery selector syntax for finding
// objects nested deeply in data.
// It's not fully featured, and can't find children, but it works well for what it does.

// Select the children of element based on tester
// If tester is not a function, use kv_typetest to create one
// Options are pass-throughed to walker.
var selector = $ = function (element, tester, opts) {
    var buf = [];

    if (!_.isFunction(tester)) {
        tester = kv_typetest(tester);
    }

    var callback = function (branch) {
        buf.push(branch);
    };

    walker(element, tester, callback, opts);

    if (buf.length === 1)
        return buf[0];

    return buf;
};
$ = selector;

// NOTES
// Selector is the third and final piece in this selection feature
// It allows one to do something like `$(nested_obj, 'hello:world')`
// to find all nodes with {hello: 'world'} in it.

// Or load('app_specific_mongorc.js');
_.mixin({
    session: function (key) {
        return db.sessions.findOne({_id: key});
    },
    invalidate_session: function (key) {
        return db.sessions.remove({_id: key});
    },
    // add your own
});

// NOTES
// This is a great place to put application-specific helper functions
// for helping you deal with the day-to-day tasks in your database.

// Autologin
auth.ro();

})();

// Finally, auto-login into read-only mode and execute the closure.

testing the script and find that isMaster.ismaster is not a function but a boolean value:
https://gist.github.com/yanatan16/6148978#file-mongorc-js-L17