JavaScript sort array by multiple (number) fields

Question

How can I implement a

 ORDER BY sort1 DESC, sort2 DESC

logic in an JSON array like such:

    var items = '[
          {
            "sort1": 1,
            "sort2": 3,
            "name" : "a",
          },
          {
            "sort1": 1,
            "sort2": 2,
            "name" : "b",
          },
          {
            "sort1": 2,
            "sort2": 1,
            "name" : "c",
          }
    ]';

resulting in the new order :

b,a,c

Answer 1

You can avoid hardcoding by create a general function

function sortByMultipleKey(keys) {
    return function(a, b) {
        if (keys.length == 0) return 0; // force to equal if keys run out
        key = keys[0]; // take out the first key
        if (a[key] < b[key]) return -1; // will be 1 if DESC
        else if (a[key] > b[key]) return 1; // will be -1 if DESC
        else return sortByMultipleKey(keys.slice(1))(a, b);
    }
}

Running

items.sort(sortByMultipleKey(['sort1', 'sort2']));

will have you

[ { sort1: 1, sort2: 2, name: 'b' },
  { sort1: 1, sort2: 3, name: 'a' },
  { sort1: 2, sort2: 1, name: 'c' } ]

Answer 2

You should design your sorting function accordingly:

items.sort(function(a, b) {
  return a.sort1 - b.sort1  ||  a.sort2 - b.sort2;
});

(because || operator has lower precedence than - one, it's not necessary to use parenthesis here).

The logic is simple: if a.sort1 - b.sort1 expression evaluates to 0 (so these properties are equal), it will proceed with evaluating || expression - and return the result of a.sort2 - b.sort2.

As a sidenote, your items is actually a string literal, you have to JSON.parse to get an array:

const itemsStr = `[{
    "sort1": 1,
    "sort2": 3,
    "name": "a"
  },
  {
    "sort1": 1,
    "sort2": 2,
    "name": "b"
  },
  {
    "sort1": 2,
    "sort2": 1,
    "name": "c"
  }
]`;
const items = JSON.parse(itemsStr);
items.sort((a, b) => a.sort1 - b.sort1 || a.sort2 - b.sort2);
console.log(items);

Answer 3

const itemsStr = `[{
    "sort1": 1,
    "sort2": 3,
    "name": "a"
  },
  {
    "sort1": 1,
    "sort2": 2,
    "name": "b"
  },
  {
    "sort1": 2,
    "sort2": 1,
    "name": "c"
  }
]`;
const items = JSON.parse(itemsStr);
items.sort((a, b) => a.sort1 - b.sort1 || a.sort2 - b.sort2);
console.log(items);