Светофор / BasicQual#3

trafficLight.js

function trafficLight() {
  var red = document.querySelector(".red");
  var yellow = document.querySelector(".yellow");
  var green = document.querySelector(".green");

  var timer = 0;

  function engine() {

    switch (timer) {
      case 0:
        red.classList.add("active");
        yellow.classList.remove("active");
        yellow.classList.add("redText");
        break;
      case 19:
        yellow.classList.remove("redText");
        yellow.classList.add("active");
        break;
      case 22:
        red.classList.remove("active");
        yellow.classList.remove("active");
        yellow.classList.add("greenText");
        green.classList.add("active");
        break;
      case 44:
        yellow.classList.add("active");
        yellow.classList.remove("greenText");
        green.classList.remove("active");
        break;
      case 47:
        trafficLight();
        break;
    }

    if (timer < 45) {
      yellow.innerHTML = (timer < 22) ? 22 - timer : 44 - timer;
    }

    timer++;
  }
  setInterval(engine, 1000);
}

trafficLight();