light_test.cpp

#include <Adafruit_NeoPixel.h>

#define PIN 2 //  D4 on nodemcu
#define NUMPIXELS 50
#define DELAYVAL 500

Adafruit_NeoPixel pixels(NUMPIXELS, PIN, NEO_RGB + NEO_KHZ800);

void setup() {
  pixels.begin();
}

void loop() {
  pixels.clear();
  for(int i=0; i<NUMPIXELS; i++) {
    pixels.setPixelColor(i, pixels.Color(255, 0, 0));
    pixels.show();
    delay(DELAYVAL);
  }
  for(int i=0; i<NUMPIXELS; i++) {
    pixels.setPixelColor(i, pixels.Color(0, 0, 0));
    pixels.show();
    delay(DELAYVAL);
  }
}

light_test2.cpp

#include <FastLED.h>

#define PIN 2 // D4 on nodemcu
#define NUMPIXELS 50
#define DELAYVAL 500

CRGB leds[NUMPIXELS];

void setup() { 
  FastLED.addLeds<WS2811, PIN, RGB>(leds, NUMPIXELS);
}

void loop() { 
  for(int i=0; i<NUMPIXELS; i++) {
    leds[i] = CRGB::Red;
    FastLED.show();
    delay(DELAYVAL);
  }
  for(int i=0; i<NUMPIXELS; i++) {
    leds[i] = CRGB::Black;
    FastLED.show();
    delay(DELAYVAL);
  }
}