Sort object collection by property's value

gistfile1.txt

arr.reduce((previous, current, index) => {
  var obj = previous;  
  var currentValue = current.label.charCodeAt(0);

  if (obj.lastValue && obj.lastValue > currentValue) {
    obj.sort.splice(index - 1, 0, current);
  } else {
    obj.sort.push(current);
  } 

  obj.lastValue = currentValue;
	
  return obj;
}, {sort:[], lastValue:null});