Sorting nested array of objects with dynamic key

Question

I am trying to create a sorting function that sorts a nested array of objects while giving a key dynamically (with different depths).

sortByKey(array, key){
    var splitKey = key.split(".");
    if(splitKey.length = 2){
      return array.sort(function(a, b) {
        var x = a[splitKey[0]][splitKey[1]]; var y = b[splitKey[0]][splitKey[1]];
        return ((x < y) ? -1 : ((x > y) ? 1 : 0));
      });
    } else {
      return array.sort(function(a, b) {
        var x = a[key]; var y = b[key];
        return ((x < y) ? -1 : ((x > y) ? 1 : 0));
      });
    }
  }

I want to get rid of the if - else and use a for loop instead. The goal is that the function works with 'name', 'name.first' and 'name.first.another' (as an example). Is there a way to do this dynamically?

In other words, I want to use the same function with different arrays. So with one array I want to sort it calling sortByKey(array1, 'name') and with another sortByKey(array2, 'location.address') and maybe with a third sortByKey(array3, 'location.address.postalcode') or something like that.

can you provide an example of what ur trying to accomplish ? — Radioreve
– Radioreve, Commented Aug 18, 2016 at 12:46

Yury Tarabanko · Accepted Answer · 2016-08-18 12:45:24Z

4

Extract property extracting function

function prop(key) {
  var keys = key.split('.');

  return keys.reduce.bind(keys, function(obj, name) {
    return obj[name]
  })
}

and use it to well extract values :)

sortByKey(array, key){
    var getKey = prop(key);

    return array.sort(function(a, b){
      var x = getKey(a); var y = getKey(b);
        return ((x < y) ? -1 : ((x > y) ? 1 : 0));
    })
  }

answered Aug 18, 2016 at 12:45

Yury Tarabanko

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9 Comments

Ricky Stam Over a year ago

This solution is so simple and elegant that deserves more up votes :)

ooo Over a year ago

.reduce.bind() (and subsequently getKey()) — Thank you for showing a good example of currying!

Nina Scholz Over a year ago

bind is not necessary here. it is superfluous and irritating. what is the actual purpose of this?

Yury Tarabanko Over a year ago

@NinaScholz "it is superfluous and irritating" well, it is your opinion. Bind wasn't that irritating back in 2016 when arrow functions required transpilation.

Nina Scholz Over a year ago

bind was neither back in time not neccessary nor today. ther is no use of this.

|

bitifet · Accepted Answer · 2016-08-18 12:46:35Z

0

I think you mean something like this:

function sortByKey(array, key){
    var splitKey = key.split(".");

    return array.sort(function(a, b) {
        var ta = a;
        var tb = b;
        for (var i=0; i<splitKey.length; i++) {
            ta = ta[splitKey[i]];
        };
        /// return ((a < b) ? -1 : ((a > b) ? 1 : 0)); // Too complex ;-)
        return a - b;

    });

};

answered Aug 18, 2016 at 12:46

bitifet

3,74919 silver badges41 bronze badges

Comments

Nina Scholz · Accepted Answer · 2022-12-30 09:55:15Z

Your problem is a misused assignment, where it should be a comparison.

if (splitKey.length === 2) {
//                  ^^^

A shorter approach could use Array#reduce.

function sortByKey(array, key) {
    var getValue = function (o, k) { return o[k]; },
        keys = key.split(".");

    return array.sort(function (a, b) {
        return keys.reduce(getValue, a) - keys.reduce(getValue, b);
    });
}

var array = [{ a: 5, b: { c: 2 } }, { a: 7, b: { c: 1 } }, { a: 1, b: { c: 3 } }];



sortByKey(array, 'a');
console.log(array);
sortByKey(array, 'b.c');
console.log(array);

ES6

function sortByKey(array, key) {
    const getValue =
        (keys => object => keys.reduce((o, k) => o[k], object))
        (key.split('.'));

    return array.sort((a, b) => getValue(a) - getValue(b));
}

var array = [{ a: 5, b: { c: 2 } }, { a: 7, b: { c: 1 } }, { a: 1, b: { c: 3 } }];

sortByKey(array, 'a');
console.log(array);
sortByKey(array, 'b.c');
console.log(array);

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