new Class() without assigning to a variable and manually deleting it via reference passed through callbacks, is it safe? Am I doing a memory leak?

I have wrote this code in NodeJS. It's a helper that works on a config file that removes some lines and rewrites that file.

Before answer, please see all marked points (with !). Each callback, returns a reference to this, that is the instance of Conf.

Here's how:

Conf.prototype.disableModem = function(modem) {
  [...]
  return this;
}

Conf.prototype.flush = function(file, cb) {
  [...]
  cb && cb(err, this);
}

I'm I safe creating it with new and passing the "pointer" through callbacks?

I don't think that the point !4 does something useful, am I right?

Am I doing a memory leak?

Any hint will be appreciated.

MyClass.prototype.disableModem = function(modem, cb) {
  this.isIdle = false; 
  async.waterfall([
    function(cb) {
      new Conf(settings.sms3.config, cb); // !1
    },
    function(conf, cb) {
      cb(null, conf.disableModem(modem)); // !2
    },
    function(conf, cb) {
      conf.flush(settings.sms3.config, cb); // !3
    },
    function(conf, cb) {
      delete conf; // !4
      this.isIdle = true;
      cb();
    }.bind(this)
  ], cb);
};