var animals = ["aligator", "bat", "cow"];
var better = document.getElementById("better");
for (var i = 0; i < animals.length; i++) {
  var input = document.createElement("input");
  input.type = "button";
  input.value = animals[i];
  input.style.marginLeft = "5px";
  (function() {
    var animal = animals[i];
    input.onclick = function() {alert(animal);};
  })();
  better.appendChild(input);
}