db-migrate/lib/driver/shadow.js

Database migration framework for node.js

/**
  * The shadow driver is basically a MITM object. Or in other words:
  *
  * This shadow is very infectius. It infects other objects and overwrite their
  * behavior. It gets a shadow part of this object and executes various
  * actions.
  *
  * In our case, it records the execution of methods.
  */

/**
  * 'Infect' the original class
  */
exports.infect = function (db, intern, ShadowProto) {
  db._shadowsHost = {};
  db._shadowProto = {};

  for (var prop in db) {
    if (
      typeof ShadowProto[prop] === 'function' &&
      typeof db[prop] === 'function'
    ) {
      db._shadowsHost[prop] = db[prop];
      db._shadowProto[prop] = ShadowProto[prop];

      (function (property) {
        db[property] = function () {
          var params = arguments;
          var self = this;

          return self._shadowProto[property]
            .apply(self, params)
            .then(function () {
              return self._shadowsHost[property].apply(self, params);
            });
        };
      })(prop);
    }
  }

  return db;
};