Push button to switching Led effects

Other Hardware LEDs and Multiplexing
40

Yes. It works perfectly. All animations change every couple of seconds. So if I think I understant this .In loop I will put milis which you sugest me yesterday.

void displayUpdate() {
  static unsigned long updateMillis;
  // 20 Hz display frame rate
  nowMillis = millis();
  if (nowMillis - updateMillis >= 50)
  {
    switch (effectState) {
      case NONE :
        noEffect();
        break;

      case BIKINI :
        pinkAndPurplePolkaDottedBikini();
        break;

      case RGB_STRIPE :
        shiftRGBStripe(1);
        break;
    }

    FastLED.show();
    updateMillis = nowMillis;
  }

}

than i will define button on beginnig of the sketch . And should working??