Most efficient way to restructure complex array of objects in javascript?

I have a large set of data that looks similar to this:

var original = [
  { country : 'us', date : '2014-10-29', cost : 45.3 },
  { country : 'africa', date : '2014-10-29', cost : 60.5 },
  { country : 'south_america', date : '2014-10-30', cost : 10 },
  { country : 'us', date : '2014-10-30', cost : 30 }
];

I need to rearrange this data so that it looks more like this:

var newData = [
  { date : '2014-10-29', us : 45.3, africa : 60.5, south_america : 0 },
  { date : '2014-10-30', us : 30, africa : 0, south_america : 10 }
]

I'm new to dealing with datasets like this and I'm struggling to find any efficient way to handle this... The only thing I can come up with uses multiple for loops and just looks gross. Does anyone have any ideas or suggestions?