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

Why are you putting your Array syntax inside (broken) string literal syntax? — I Hate Lazy
– I Hate Lazy, Commented Nov 3, 2012 at 17:39
Since you're assigning the Array to the items variable, you're already in a JavaScript environment, so it doesn't make too much sense to first represent it as JSON markup, then parse it. If that was meant to represent JSON markup being sent from the server, then a better representation is to get rid of the extra var items = ...; syntax, and just show it as markup with a note explaining that it's your server side markup. — I Hate Lazy
– I Hate Lazy, Commented Nov 3, 2012 at 17:46
Possible duplicate of Sort by two values prioritizing on one of them — Boris Yakubchik
– Boris Yakubchik, Commented Aug 24, 2019 at 14:52

raina77ow · Accepted Answer · 2018-04-02 10:43:35Z

115

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);

edited Apr 2, 2018 at 10:43

answered Nov 3, 2012 at 17:37

raina77ow

107k16 gold badges205 silver badges240 bronze badges

Sign up to request clarification or add additional context in comments.

8 Comments

xhg Over a year ago

using operator - might cause problem since the value might be strings.

raina77ow Over a year ago

I'm afraid you miss the point here, both in your comment and in your answer. Using - instead of < is the way to enforce comparing the operands as numbers, not as strings. Remember, '12' < '3' evaluates to true in JavaScript.

xhg Over a year ago

That’s exactly what I am saying. - only applies to numbers. I am not saying you are wrong. I am providing a general solution as I said in my answer.

xhg Over a year ago

‘12’ should be less than ‘3’.

raina77ow Over a year ago

Remember, explicit is better than implicit. If you want values to be compared as strings in any case, use String.localeCompare() instead. < is ambiguous; its result depends on operands types - and type juggling, if those are different.

|

xhg · Accepted Answer · 2017-11-22 00:24:38Z

9

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' } ]

answered Nov 22, 2017 at 0:24

xhg

1,9033 gold badges22 silver badges36 bronze badges

1 Comment

raina77ow Over a year ago

Sorry to say, but this implementation of generic function is way too inefficient. Not only using recursion here is dubious (you can just iterate over list of keys until comparison results in non-zero), for each 'comparison miss' there's a new instance of comparison function generated. Compare your code to lodash implementation, for example.

Fernando Lucas Souza · Accepted Answer · 2019-11-22 02:36:09Z

0

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);

answered Nov 22, 2019 at 2:36

Fernando Lucas Souza

11 bronze badge

Collectives™ on Stack Overflow

JavaScript sort array by multiple (number) fields

3 Answers 3

8 Comments

1 Comment

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

8 Comments

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related