var mongoose = require('mongoose');
mongoose.connect('mongodb://localhost/so-39683097');
var db = mongoose.connection;
db.on('error', console.error.bind(console, 'connection error:'));
db.once('open', function() {
  var photosSchema = mongoose.Schema({
    username:{
      type: String
    },
    photo: {
      type: String
    },
    caption: {
      type: String
    },
    approved: {
      type: Number,
      default: 0
    }
  });
  photosSchema.statics.getApprovedPhotos = function(username, cb){
    this.find({username: username, approved:1}).sort({'_id': 1}).exec(cb);
  };
  var Photo = mongoose.model('Photo', photosSchema);
  var p1 = new Photo({username:'demo', approved:0});
  var p2 = new Photo({username:'demo', approved:1});
  p1.save(function (err, p1) {
    p2.save(function (err, p2) {
      Photo.getApprovedPhotos('demo', function (err, photos) {
        console.log(photos);
      });
    });
  });
});

/*
Output:

[ { _id: 57e74d6a637a9a39f24fdc70,
    username: 'demo',
    __v: 0,
    approved: 1 } ]

*/