document.querySelectorAll('button').forEach(function(button) {
  button.addEventListener('mouseenter', function() {
    function random(max) {
      return Math.random() * (max - 0) + 0;
    }

    var c = document.createDocumentFragment();
    for (var i = 0; i < 100; i++) {
      var styles = 'transform: translate3d(' + (random(500) - 250) + 'px, ' +
                   (random(200) - 150) + 'px, 0) rotate(' + random(360) + 'deg);' +
                   'background: hsla(' + random(360) + ', 100%, 50%, 1);' +
                   'animation: bang 700ms ease-out forwards;' +
                   'opacity: 0';

      var e = document.createElement("i");
      e.style.cssText = styles;
      c.appendChild(e);
    }
    button.appendChild(c);
  });
});