Find a unique item in an array.

unique.js

  var orig = [1,1,2,2,3,3,4];
  var result;
  orig.forEach(function(num, i){
      var test = orig.slice(0); 
      test.splice(i, 1)
      if(test.indexOf(num) === -1){
          result = num;
      }
  });
 return result; // 4