Reduce array of objects on key and sum value into array

You can get all the unique names using map() and uniq(), and then map() each name to get their respective sums using sumBy().

var data = [
  { name: 'foo', type: 'fizz', val: 9 },
  { name: 'foo', type: 'buzz', val: 3 },
  { name: 'bar', type: 'fizz', val: 4 },
  { name: 'bar', type: 'buzz', val: 7 }
];

var result = _(data)
  .map('name')
  .uniq()
  .map(key => ({ 
    key, 
    val: _(data).filter({ name: key }).sumBy('val')
  }))
  .value();

console.log(result);