Merge and sort two object arrays in Javascript

Question

I have two arrays and depending on the element's position in the array it receives a value. Both arrays contain the same elements, but at different positions. I would like to calculate the value for each element, merge the arrays into a single array, and sort the new array.

The only idea I can think of is to turn my initial arrays into arrays of objects, merge those, sort by object value, then map that order into a new array.

var ranks = [],
    objArray1 = [],
    objArray2 = [];

// 'aaa' = 5, 'bbb' = 4, 'ddd' = 3, 'eee' = 2, 'ccc' = 1
var array1 = ['aaa', 'bbb', 'ddd', 'eee', 'ccc'];

// 'ddd' = 5, 'ccc' = 4, 'aaa' = 3, 'bbb' = 2, 'eee' = 1
var array2 = ['ddd', 'ccc', 'aaa', 'bbb', 'eee'];

for (var i = 0, x = 5; i < 5; x--, i++) {
  var obj = {};
  obj[array1[i]] = x;
  objArray1.push(obj);
}

for (var i = 0, x = 5; i < 5; x--, i++) {
  var obj = {};
  obj[array2[i]] = x;
  objArray2.push(obj);
}

// combine both object arrays, match keys, but add values
// should output ranks =[{aaa: 8}, {bbb: 6}, {ccc: 5}, {ddd: 8}, {eee: 3}]

// then sort based on value
// should output ranks = [{aaa: 8}, {ddd: 8}, {bbb: 6}, {ccc: 5}, {eee: 3}]

// then copy keys over to new array while keeping position
// should output var final = ['aaa', 'ddd', 'bbb', 'ccc', 'eee']

You just wanna sort the elements by their sum over both arrays? — sam46
– sam46, Commented Dec 27, 2017 at 19:54

Nina Scholz · Accepted Answer · 2017-12-27 20:25:34Z

2

You could skip the part with new temporary arrays with objects and take just an object for counting and then take the sorted keys as result.

var array1 = ['aaa', 'bbb', 'ddd', 'eee', 'ccc'],
    array2 = ['ddd', 'ccc', 'aaa', 'bbb', 'eee'],
    temp = Object.create(null),
    result;

[array1, array2].forEach(a => a.forEach((k, i) => temp[k] = (temp[k] || 0) - i));
result = Object.keys(temp).sort((a, b) => temp[b] - temp[a]);

console.log(result);

edited Dec 27, 2017 at 20:25

answered Dec 27, 2017 at 20:02

Nina Scholz

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1 Comment

itsclarke Over a year ago

Hey that's really clever! Many thanks! The solution I was working on was just a mess of loops, this is much cleaner.

Nenad Vracar · Accepted Answer · 2017-12-27 20:23:40Z

1

You could use reduce to create object and then use sort on Object.keys.

const array1 = ['aaa', 'bbb', 'ddd', 'eee', 'ccc'];
const array2 = ['ddd', 'ccc', 'aaa', 'bbb', 'eee'];
const n = array1.length;

const r = array1.reduce((r, e, i) => (r[e] = n - i + n - array2.indexOf(e), r), {})
const result = Object.keys(r).sort((a, b) => r[b] - r[a])
console.log(result)

edited Dec 27, 2017 at 20:23

answered Dec 27, 2017 at 20:02

Nenad Vracar

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