How to sort an array of objects by multiple fields?

Question

From this original question, how would I apply a sort on multiple fields?

Using this slightly adapted structure, how would I sort city (ascending) & then price (

Answer 1

This is a complete cheat but I think that it adds value to this question because it's basically a canned library function that you can use out-of-the box.

If your code has access to lodash or a lodash compatible library like underscore then you can use the _.sortBy method. The snippet below is copied directly from the lodash documentation.

The commented results in the examples looks like they return arrays of arrays but that's just showing the order and not the actual results which are an array of objects.

var users = [
  { 'user': 'fred',   'age': 48 },
  { 'user': 'barney', 'age': 36 },
  { 'user': 'fred',   'age': 40 },
  { 'user': 'barney', 'age': 34 }
];

_.sortBy(users, [function(o) { return o.user; }]);
 // => objects for [['barney', 36], ['barney', 34], ['fred', 48], ['fred', 40]]

_.sortBy(users, ['user', 'age']);
// => objects for [['barney', 34], ['barney', 36], ['fred', 40], ['fred', 48]]

Answer 2

Here 'AffiliateDueDate' and 'Title' are columns, both are sorted in ascending order.

array.sort(function(a, b) {

               if (a.AffiliateDueDate > b.AffiliateDueDate ) return 1;
               else if (a.AffiliateDueDate < b.AffiliateDueDate ) return -1;
               else if (a.Title > b.Title ) return 1;
               else if (a.Title < b.Title ) return -1;
               else return 0;
             })

Answer 3

Another way

var homes = [
    {"h_id":"3",
     "city":"Dallas",
     "state":"TX",
     "zip":"75201",
     "price":"162500"},
    {"h_id":"4",
     "city":"Bevery Hills",
     "state":"CA",
     "zip":"90210",
     "price":"319250"},
    {"h_id":"6",
     "city":"Dallas",
     "state":"TX",
     "zip":"75000",
     "price":"556699"},
    {"h_id":"5",
     "city":"New York",
     "state":"NY",
     "zip":"00010",
     "price":"962500"}
    ];
function sortBy(ar) {
  return ar.sort((a, b) => a.city === b.city ?
      b.price.toString().localeCompare(a.price) :
      a.city.toString().localeCompare(b.city));
}
console.log(sortBy(homes));

Answer 4

Here is a simple functional approach. Specify sort order using array. Prepend minus to specify descending order.

var homes = [
    {"h_id":"3", "city":"Dallas", "state":"TX","zip":"75201","price":"162500"},
    {"h_id":"4","city":"Bevery Hills", "state":"CA", "zip":"90210", "price":"319250"},
    {"h_id":"6", "city":"Dallas", "state":"TX", "zip":"75000", "price":"556699"},
    {"h_id":"5", "city":"New York", "state":"NY", "zip":"00010", "price":"962500"}
    ];

homes.sort(fieldSorter(['city', '-price']));
// homes.sort(fieldSorter(['zip', '-state', 'price'])); // alternative

function fieldSorter(fields) {
    return function (a, b) {
        return fields
            .map(function (o) {
                var dir = 1;
                if (o[0] === '-') {
                   dir = -1;
                   o=o.substring(1);
                }
                if (a[o] > b[o]) return dir;
                if (a[o] < b[o]) return -(dir);
                return 0;
            })
            .reduce(function firstNonZeroValue (p,n) {
                return p ? p : n;
            }, 0);
    };
}

Edit: in ES6 it's even shorter!

"use strict";
const fieldSorter = (fields) => (a, b) => fields.map(o => {
    let dir = 1;
    if (o[0] === '-') { dir = -1; o=o.substring(1); }
    return a[o] > b[o] ? dir : a[o] < b[o] ? -(dir) : 0;
}).reduce((p, n) => p ? p : n, 0);

const homes = [{"h_id":"3", "city":"Dallas", "state":"TX","zip":"75201","price":162500},     {"h_id":"4","city":"Bevery Hills", "state":"CA", "zip":"90210", "price":319250},{"h_id":"6", "city":"Dallas", "state":"TX", "zip":"75000", "price":556699},{"h_id":"5", "city":"New York", "state":"NY", "zip":"00010", "price":962500}];
const sortedHomes = homes.sort(fieldSorter(['state', '-price']));

document.write('<pre>' + JSON.stringify(sortedHomes, null, '\t') + '</pre>')

Answer 5

A multi dimensional sorting method, based on this answer:

Update: Here is an "optimized" version. It does a lot more preprocessing and creates a comparison function for each sorting option beforehand. It might need more more memory (as it stores a function for each sorting option, but it should preform a bit better as it does not have to determine the correct settings during the comparison. I have not done any profiling though.

var sort_by;

(function() {
    // utility functions
    var default_cmp = function(a, b) {
            if (a == b) return 0;
            return a < b ? -1 : 1;
        },
        getCmpFunc = function(primer, reverse) {
            var dfc = default_cmp, // closer in scope
                cmp = default_cmp;
            if (primer) {
                cmp = function(a, b) {
                    return dfc(primer(a), primer(b));
                };
            }
            if (reverse) {
                return function(a, b) {
                    return -1 * cmp(a, b);
                };
            }
            return cmp;
        };

    // actual implementation
    sort_by = function() {
        var fields = [],
            n_fields = arguments.length,
            field, name, reverse, cmp;

        // preprocess sorting options
        for (var i = 0; i < n_fields; i++) {
            field = arguments[i];
            if (typeof field === 'string') {
                name = field;
                cmp = default_cmp;
            }
            else {
                name = field.name;
                cmp = getCmpFunc(field.primer, field.reverse);
            }
            fields.push({
                name: name,
                cmp: cmp
            });
        }

        // final comparison function
        return function(A, B) {
            var a, b, name, result;
            for (var i = 0; i < n_fields; i++) {
                result = 0;
                field = fields[i];
                name = field.name;

                result = field.cmp(A[name], B[name]);
                if (result !== 0) break;
            }
            return result;
        }
    }
}());

Example usage:

homes.sort(sort_by('city', {name:'price', primer: parseInt, reverse: true}));

DEMO

---

Original function:

var sort_by = function() {
   var fields = [].slice.call(arguments),
       n_fields = fields.length;

   return function(A,B) {
       var a, b, field, key, primer, reverse, result, i;

       for(i = 0; i < n_fields; i++) {
           result = 0;
           field = fields[i];

           key = typeof field === 'string' ? field : field.name;

           a = A[key];
           b = B[key];

           if (typeof field.primer  !== 'undefined'){
               a = field.primer(a);
               b = field.primer(b);
           }

           reverse = (field.reverse) ? -1 : 1;

           if (a<b) result = reverse * -1;
           if (a>b) result = reverse * 1;
           if(result !== 0) break;
       }
       return result;
   }
};

DEMO

Answer 6

I was looking for something similar and ended up with this:

First we have one or more sorting functions, always returning either 0, 1 or -1:

const sortByTitle = (a, b): number => 
  a.title === b.title ? 0 : a.title > b.title ? 1 : -1;

You can create more functions for each other property you want to sort on.

Then I have a function that combines these sorting functions into one:

const createSorter = (...sorters) => (a, b) =>
  sorters.reduce(
    (d, fn) => (d === 0 ? fn(a, b) : d),
    0
  );

This can be used to combine the above sorting functions in a readable way:

const sorter = createSorter(sortByTitle, sortByYear)

items.sort(sorter)

When a sorting function returns 0 the next sorting function will be called for further sorting.