extending the API about esp8266-homekit

[AdySan]

Just to understand your question better, let me pull an example from HAP-NodeJS.

/**
 * Characteristic "Brightness"
 */

Characteristic.Brightness = function() {
  Characteristic.call(this, 'Brightness', '00000008-0000-1000-8000-0026BB765291');
  this.setProps({
    format: Characteristic.Formats.INT,
    unit: Characteristic.Units.PERCENTAGE,
    maxValue: 100,
    minValue: 0,
    minStep: 1,
    perms: [Characteristic.Perms.READ, Characteristic.Perms.WRITE, Characteristic.Perms.NOTIFY]
  });
  this.value = this.getDefaultValue();
};

inherits(Characteristic.Brightness, Characteristic);

Characteristic.Brightness.UUID = '00000008-0000-1000-8000-0026BB765291';

Brightness has a relatively simple structure, but your concern in that other characteristics might have more parameters. As an example CurrentHeatingCoolingState.

/**
 * Characteristic "Current Heating Cooling State"
 */

Characteristic.CurrentHeatingCoolingState = function() {
  Characteristic.call(this, 'Current Heating Cooling State', '0000000F-0000-1000-8000-0026BB765291');
  this.setProps({
    format: Characteristic.Formats.UINT8,
    perms: [Characteristic.Perms.READ, Characteristic.Perms.NOTIFY]
  });
  this.value = this.getDefaultValue();
};

inherits(Characteristic.CurrentHeatingCoolingState, Characteristic);

Characteristic.CurrentHeatingCoolingState.UUID = '0000000F-0000-1000-8000-0026BB765291';

// The value property of CurrentHeatingCoolingState must be one of the following:
Characteristic.CurrentHeatingCoolingState.OFF = 0;
Characteristic.CurrentHeatingCoolingState.HEAT = 1;
Characteristic.CurrentHeatingCoolingState.COOL = 2;

Are you asking for a way to deal with all such characteristics in a single function addCharacteristic?

[HomeACcessoryKid]

Actually when I opened this issue, I was not aware of how the HomeKit philosophy works. But actually the issue does not exist and the current approach is already OK.
Basic idea is that each type of characteristic has its build in variables, predefined for this very characteristic. So they go statically inside the API and the outside user has not to worry about them.

I will close the issue...