gistfile1.txt

// References

[
  {
    "id": "0001",
    "qty": 0,
  },
  {
    "id": "0002",
    "qty": 0,
  }
]

// Transactions

[
  {
    "id": "0001",
    "qty": 42,
    "otherstuff": "blah blah"
  },
  {
    "id": "0001",
    "qty": 8,
  },
  {
    "id": "0002",
    "qty": 20,
    "otherstuff": "ignore me"
  },
]

// Expected Outputs

[
  {
    "id": "0001",
    "qty": 50,
  },
  {
    "id": "0002",
    "qty": 20,
  }
]