index.js

/**
 * Add all items in an array of numbers.
 */
function addArray(array) {
  return array.reduce((a, b) => a + b)
}

/**
 * Calculate total stats (keyed by category), then generate
 * additional meta stats based on initial calculations.
 */
function calculateTotals(input) {
  return Object.entries(input)
    .reduce((accumulator, [key, values], index, array) => {
      accumulator[key] = addArray(values)

      if (index === (array.length - 1)) {
        const allValues = Object.values(accumulator)

        accumulator.all = addArray(allValues)
      }

      return accumulator
    }, {})
}

// Result:
calculateTotals({
  cats: [1, 2, 3, 4, 5],
  dogs: [6, 7, 8, 9, 10],
})
// {
//   cats: 15,   // 1 + 2 + 3 + 4 + 5
//   dogs: 40,   // 6 + 7 + 8 + 9 + 10
//   total: 55,  // 15 + 40
// }