JavaScript: Sort array of objects by computed property or by an existing property if equal

Question

[
    { name: 'Joe', scores: [1, 2, 3] },
    { name: 'Jane', scores: [1, 2, 3] },
    { name: 'John', scores: [1, 2, 3] }
]

how do I make a function that sorts the elements first by the sum in scores and later by name?

Answer 1

You could take a Map for all sums and the object as key without mutating data.

const
    data = [{ name: 'Joe', scores: [1, 2, 3] }, { name: 'Jane', scores: [1, 4, 3] }, { name: 'John', scores: [1, 2, 1] }],
    add = (a, b) => a + b,
    sums = new Map(data.map(o => [o, o.scores.reduce(add, 0)]));

data.sort((a, b) => sums.get(b) - sums.get(a) || a.name.localeCompare(b.name));

console.log(data);

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Answer 2

The lodash package could be handy

const lodash = require('lodash')

const list = [
  { name: 'Joe', scores: [1, 2, 4] },
  { name: 'Jane', scores: [1, 2, 3] },
  { name: 'John', scores: [1, 2, 4] }
]

const listWithSum = list.map(item => {
  return {
    ...item,
    sum: lodash.sum(item.scores)
  }
})

const sortedList = lodash.orderBy(listWithSum, ['score', 'name'], ['desc', 'desc'])

console.log(sortedList)