Sort array of object for some keys in javascript

Question

I have one array of object like.

[{
  id: 1,
  age: 23
}, {
  id: 1,
  age: 25
}, {
  id: 2,
  age: 230
}, {
  id: 2,
  age: 255
}, {
  id: 3,
  age: 232
}, {
  id: 1,
  age: 215
}]

I need to get the final array by sorting with hightest age for each id. so final array will be.

[{
    id: 1,
    age: 215
  }, {
    id: 2,
    age: 255
  }, {
    id: 3,
    age: 232
  }]

In what way is your desired output example sorted? And why do you have duplicate IDs? — Jamie, May 06 '16 at 15:51
http://stackoverflow.com/questions/14446511/what-is-the-most-efficient-method-to-groupby-on-a-javascript-array-of-objects — vvg, May 06 '16 at 15:53
its just sample data. i just simplified it that for same id we can have different age values. — Rahul Tailwal, May 06 '16 at 15:54

score 1 · Answer 1 · answered May 06 '16 at 15:56

You can build a hash in which you store the object with the maximum age for each id. Then sort its keys numerically and get the values in that order.

var hash = array.reduce(function(hash, obj) {
  if(!hash[obj.id]) hash[obj.id] = obj;
  else if(hash[obj.id].age < obj.age) hash[obj.id] = obj;
  return hash;
}, Object.create(null));
Object.keys(hash).sort(function(a,b) {
  return a - b;
}).map(function(id) {
  return hash[id];
});

score 0 · Answer 2 · answered May 06 '16 at 16:16

a single liner here

var arr = [{
  id: 1,
  age: 23,
}, {
  id: 1,
  age: 25,
}, {
  id: 2,
  age: 230,
}, {
  id: 2,
  age: 255,
}, {
  id: 3,
  age: 232,
}, {
  id: 1,
  age: 215,
}],
lut = {},
res = arr.sort((a,b) => b.age - a.age).filter(o => lut[o.id] ? false : lut[o.id] = true).sort((a,b) => a.id - b.id);

document.write("<pre>" + JSON.stringify(res,null,2) + "</pre>");

score 0 · Answer 3 · edited May 23 '17 at 11:52

You would normally use filter with indexOf to remove duplicate elements from an array. In the case when array elements are objects, you can use findIndex to search for the index of a element by some given property values.

let result = [{
  id: 1,
  age: 23,
}, {
  id: 1,
  age: 25,
}, {
  id: 2,
  age: 230,
}, {
  id: 2,
  age: 255,
}, {
  id: 3,
  age: 232,
}, {
  id: 1,
  age: 215,
}].sort((a,b) => b.age - a.age)
.filter((row,pos,self) => self.findIndex(item => item.id === row.id) === pos)
.sort((a,b) => a.id - b.id);

document.body.textContent = JSON.stringify(result);

Also, you need to pay attention to its browser support.

score 0 · Answer 4 · answered May 06 '16 at 17:05

0

or this way to avoid using lodash's uniq() method:

arr.sort(function(a,b){
  return b.id > a.id;
}).reverse();
var max = arr.length;
var i = 0;
while(i < max - 1){
  if (arr[i].id === arr[i+1].id) arr.splice(i+1,1);
  else i++
  max = arr.length;
}

answered May 06 '16 at 17:05

kevin ternet

4,514
2
19
27

score 0 · Answer 5 · answered May 07 '16 at 17:51

0

You can do sorting this way Using vanillaJS.

function sortByAgeDesc(a,b) {return a.age > b.age ? -1 : a.age === b.age ? 0 : 1;}


output = input.sort(sortByAgeDesc);

Now the question is you want only distinct ids.

answered May 07 '16 at 17:51

Devank

159
2
9

Sort array of object for some keys in javascript

5 Answers5