script.js

var block = document.getElementById("block");
var hole = document.getElementById("hole");
var character = document.getElementById("character");
var jumping = 0;
var counter = 0;

hole.addEventListener('animationiteration', () => {
  var random = -((Math.random() * 300) + 150);
  hole.style.top = random + "px";
  counter++;
});
setInterval(function () {
  var characterTop = parseInt(window.getComputedStyle(character).getPropertyValue("top"));
  if (jumping == 0) {
    character.style.top = (characterTop + 3) + "px";
  }
  var blockLeft = parseInt(window.getComputedStyle(block).getPropertyValue("left"));
  var holeTop = parseInt(window.getComputedStyle(hole).getPropertyValue("top"));
  var cTop = -(500 - characterTop);
  if ((characterTop > 480) || ((blockLeft < 20) && (blockLeft > -50) && ((cTop < holeTop) || (cTop > holeTop + 130)))) {
    alert("Game over. Score: " + (counter - 1));
    character.style.top = 100 + "px";
    counter = 0;
  }
}, 10);

function jump() {
  jumping = 1;
  let jumpCount = 0;
  var jumpInterval = setInterval(function () {
    var characterTop = parseInt(window.getComputedStyle(character).getPropertyValue("top"));
    if ((characterTop > 6) && (jumpCount < 15)) {
      character.style.top = (characterTop - 5) + "px";
    }
    if (jumpCount > 20) {
      clearInterval(jumpInterval);
      jumping = 0;
      jumpCount = 0;
    }
    jumpCount++;
  }, 10);
}