jQuery jAM, Season 6

	 
var ancestry = JSON.parse(ANCESTRY_FILE);

function average(array) {
  function plus(a, b) { 
  		return a + b; 
  		}
  	return array.reduce(plus) / array.length;
}

function groupBy(array, groupOf) {
  var groups = {};
  array.forEach(function(element) {
    var groupName = groupOf(element);
    if (groupName in groups)
      groups[groupName].push(element);
    else
      groups[groupName] = [element];
  });
   return groups;
}

var byCentury = groupBy(ancestry, function(person) {
  	return Math.ceil(person.died / 100);
});

for (var century in byCentury) {
  var ages = byCentury[century].map(function(person) {
    	return person.died - person.born;
  });
 
 
  console.log(century + ": " + average(ages));
}