Saving modules and using saved functions?

Hello
Is it somehow possible to call a function you have saved on the ESP8266??

For example:
I would like to save the stepper module on the ESP8266 so I am able to do stuff like:

var motorLeft = new StepperMotor({
  pins:[D0,D2,D4,D5],
  pattern:[0b0010,0b0001,0b0100,0b1000]
});

without having to get the module off the web and upload it everytime.
The problem with this is that if I connect to the ESP8266 over wifi, my computer is no longer connected to the web and can therefore no longer get the module.

And also, would it be possible to save something like this:

function forward(steps) {
  motorRight.moveTo(motorRight.getPosition­()+steps, 1);
  motorLeft.moveTo(motorLeft.getPosition()­-steps, 1);
}

to the ESP8266, so that I can just send something like this: forward(1000);

Thanks :)