How to Group and Sum an Array of Objects by a Key in JavaScript?

Grouping and Summing an Array of Objects by a Key

In JavaScript, you can group an array of objects by a specific key and sum the values associated with that key using jQuery's powerful tools. Here's how you can achieve this:

var array = [
  { Id: '001', qty: 1 },
  { Id: '002', qty: 2 },
  { Id: '001', qty: 2 },
  { Id: '003', qty: 4 }
];

Looping and Summing

One effective method is to iterate through the array and accumulate the values using the reduce() method. This method takes a callback function that reduces the array to a single value, in this case, an object representing the grouped values.

var result = [];
array.reduce(function (res, value) {
  if (!res[value.Id]) {
    res[value.Id] = { Id: value.Id, qty: 0 };
    result.push(res[value.Id]);
  }
  res[value.Id].qty += value.qty;
  return res;
}, {});

Output:

[
  { Id: '001', qty: 3 },
  { Id: '002', qty: 2 },
  { Id: '003', qty: 4 }
]

This solution efficiently groups the objects by the Id key and sums the corresponding qty values, resulting in an array of objects with grouped and summed values.

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