Remove dups from an array in Javascript

dedupe.js

var arr = [9, 9, 111, 2, 3, 4, 4, 5, 7];
var sorted_arr = arr.sort();
var results = [];
for (var i = 0; i < arr.length - 1; i += 1) {
  if (sorted_arr[i + 1] == sorted_arr[i]) {
    results.push(sorted_arr[i]);
  }
}
alert(results);

# or

function eliminateDuplicates(arr) {
  var i,
      len=arr.length,
      out=[],
      obj={};

  for (i=0;i<len;i++) {
    obj[arr[i]]=0;
  }
  for (i in obj) {
    out.push(i);
  }
  return out;
}