function InitButton() {
  let button4 = document.getElementById('button4');
  button4.addEventListener("click", Button4);
}

function randSize(itemId) {
  let item = document.getElementById(itemId);

  item.style.width = Math.floor(Math.random() * Math.floor(120)) + 'px';
  item.style.height = Math.floor(Math.random() * Math.floor(120)) + 'px';
}

function Button4() {
  randSize("box1");
  randSize("box2");
  randSize("box3");
}

InitButton();