问Arduino怎么在for循环中用millis替代delay函数，实现依次点亮ws2812灯珠？

#include <FastLED.h>
#define NUM_LEDS 9
#define DATA_PIN 4

CRGB leds[NUM_LEDS];
void setup() {
   	delay(2000);
    FastLED.addLeds<WS2811, DATA_PIN, GRB>(leds, NUM_LEDS);

}

void flash2812(){
for(int flashLed = 0;flashLed < NUM_LEDS; flashLed = flashLed + 1) {
      leds[flashLed] = CRGB::Green;
      FastLED.show();
        delay(100);
      leds[flashLed] = CRGB::Black;
  }         
    
}


void loop() {
  flash2812();
}