SOURCE

var arr = [3,6,3,5,2,7,6,7,9];
var list = singleNumbers(arr);
console.log(list);


function singleNumbers (arr) {
  arr.sort();
  var list = [];  // 保存单个的元素
  for (var i = 0; i < arr.length;) {
    if (i + 1 >= arr.length) {
      list.push(arr[i]);
      break;
    }
    if (arr[i] == arr[i+1]) {
      i = i + 2;
    } else {
      list.push(arr[i]);
      i = i + 1;
    }
  }
  return list;
}