custom sort order on array of objects

Question

I know we can define our custom sort function of array of json objects. But what if the order is neither desc nor asc. For example lets say my array looks like:

[ {
    name: 'u'
  },
  {
    name: 'n'
  },
  {
    name: 'a'
  },
  { 
    name: 'n',
  } 
]

Output should look like:

[ {
    name: 'n'
  },
  {
    name: 'n'
  },
  {
    name: 'a'
  },
  { 
    name: 'u',
  } 
]

Where all the names starting with n are sorted first and then the rest. I have tried the following custom sort function:

_sortByName(a, b){
        if (a.name === 'n'){
            return 1;
        } else if(b.name === 'n'){
            return 1;
        } else if(a.name < b.name){
            return 1;
        } else if(a.name > b.name){
            return -1;
        }
    }

But the order returned for objects is wrong. What is going wrong here?

if (a.name === 'n') and if (b.name === 'n') both return 1, which appears to be incorrect. — zzzzBov
– zzzzBov, Commented Jul 5, 2016 at 19:50

Vikasdeep Singh · Accepted Answer · 2018-07-17 13:48:04Z

44

If you have an arbitrary sort order, one option is to assign the order to an array and then use indexOf:

var sortOrder = ['n', 'a', 'u'];
var myArray = [{
    name: 'u'
  },
  {
    name: 'n'
  },
  {
    name: 'a'
  },
  {
    name: 'n'
  }
];
myArray.sort(function(a, b) {
  return sortOrder.indexOf(a.name) - sortOrder.indexOf(b.name);
});

console.log(myArray);

If you have many values in either array, it might be worthwhile creating a value-index map first and then using sortOrder[a.name].

edited Jul 17, 2018 at 13:48

Vikasdeep Singh

21.9k16 gold badges82 silver badges106 bronze badges

answered Jul 5, 2016 at 19:53

nrabinowitz

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Comments

DecPK · Accepted Answer · 2021-10-25 09:00:00Z

1) You can use indexOf here

const dict = "nau";
var myArray = [
  {
    name: "u",
  },
  {
    name: "n",
  },
  {
    name: "a",
  },
  {
    name: "n",
  },
];

myArray.sort((a, b) => dict.indexOf(a.name) - dict.indexOf(b.name));

console.log(myArray);

/* This is not a part of answer. It is just to give the output full height. So IGNORE IT */
.as-console-wrapper { max-height: 100% !important; top: 0; }

2) You can use Map here

I've added some gap/space in between two character because there can be other character that will come between them, so you can place in between them

const order = {
  n: 100,
  a: 200,
  u: 300,
};

var myArray = [
  {
    name: "u",
  },
  {
    name: "n",
  },
  {
    name: "a",
  },
  {
    name: "n",
  },
];
myArray.sort((a, b) => order[a.name] - order[b.name]);

console.log(myArray);

/* This is not a part of answer. It is just to give the output full height. So IGNORE IT */
.as-console-wrapper { max-height: 100% !important; top: 0; }

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