<script>
var dictionary = {
  "cats": [1, 2, 37, 38, 40, 32, 33, 35, 39, 36],
  "dogs": [4, 5, 6, 3, 2]
};

// Get the keys
var keys = Object.keys(dictionary);

console.log(keys);

for (var key in dictionary) {
	console.log("key:", key);
  if (dictionary.hasOwnProperty(key)) {
    keys.push(key);
  }
}

</script>