数组去重（uniq）

array uniq

function uniq (arr1, arr2) {
  var result = arr1.concat(arr2)
    , len = result.length;
    
  for (var i = 0; i < len; i++) {
    var firstIdx = result.indexOf(result[i])
      , lastIdx = result.lastIndexOf(result[i]);
    while (firstIdx !== lastIdx) {
      result.splice(lastIdx, 1);
      len = len - 1;
      firstIdx = result.indexOf(result[i]);
      lastIdx = result.lastIndexOf(result[i]);
    }
  }
  return result;
}

var a = [1, 10, 5, 8, 4]
  , b = [5, 2, 5, 7, 84, 1];
console.log(uniq(a, b));  // [ 1, 10, 5, 8, 4, 2, 7, 84 ]