Difference between two array when elements are array

Question

var a = [["Green","Medium"],["Green","Small"],["Medium","Red"],["Red","Small"]];

var b = [["Green","Medium"],["Green","Small"],["Medium","Red"]];

So my result will [["Red","Small"]]

Not that a.filter(x => !b.includes(x)) won't work because all element are array. I've tried something like that

    var diff = [];
    a.forEach((res, i) => {
      b.forEach((res2, j) => {
        if (i === j && !_.isEqual(res, res2)) {
          diff.push(res);
        }
      });
    });
console.log(diff);

This not working when different elements are last positions

Will a always contain more (or the same) elements as b?

CertainPerformance
– CertainPerformance

2018-12-27 05:32:26 +00:00
Commented Dec 27, 2018 at 5:32 — CertainPerformance
– CertainPerformance, Commented Dec 27, 2018 at 5:32
@CertainPerformance yes

Imran
– Imran

2018-12-27 05:32:55 +00:00
Commented Dec 27, 2018 at 5:32 — Imran
– Imran, Commented Dec 27, 2018 at 5:32

Robby Cornelissen · Accepted Answer · 2018-12-27 05:37:53Z

3

In lodash, you can use _.differenceWith() and supply _.isEqual() as a comparator to perform a deep comparison:

const c = _.differenceWith(a, b, _.isEqual);

Full snippet:

const a = [["Green","Medium"],["Green","Small"],["Medium","Red"],["Red","Small"]];
const b = [["Green","Medium"],["Green","Small"],["Medium","Red"]];

const c = _.differenceWith(a, b, _.isEqual);

console.log(c);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.11/lodash.min.js"></script>

answered Dec 27, 2018 at 5:37

Robby Cornelissen

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Comments

CertainPerformance · Accepted Answer · 2018-12-27 05:35:21Z

2

For an O(N) solution that doesn't require a library, I'd map b to a Set of strings by stringifying the contents of each sub-array, then filter a by whether a's stringified items are contained in the set:

var a = [["Green","Medium"],["Green","Small"],["Medium","Red"],["Red","Small"]];
var b = [["Green","Medium"],["Green","Small"],["Medium","Red"]];

const bSet = new Set(b.map(arr => JSON.stringify(arr)));
const aFiltered = a.filter(arr => !bSet.has(JSON.stringify(arr)));
console.log(aFiltered);

(Set.has is generally O(1), unlike Array methods like includes and indexOf)

answered Dec 27, 2018 at 5:35

CertainPerformance

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1 Comment

Imran Over a year ago

Yes. I like this technique without lodash. Thank you

Just code · Accepted Answer · 2018-12-27 05:37:07Z

2

As you are already using lodash you can use combination of filter and every to compare two array.

var a = [["Green","Medium"],["Green","Small"],["Medium","Red"],["Red","Small"]];

var b = [["Green","Medium"],["Green","Small"],["Medium","Red"]];


var unique = a.filter(a=> b.every(b=> !_.isEqual(a, b)));
console.log(unique)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.js"></script>

answered Dec 27, 2018 at 5:37

Just code

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Comments

Manoj · Accepted Answer · 2018-12-27 05:38:13Z

0

var a = [["Green","Medium"],["Green","Small"],["Medium","Red"],["Red","Small"]];

var b = [["Green","Medium"],["Green","Small"],["Medium","Red"]];

var c = b.map(ele=>JSON.stringify(ele));

var p = a.filter(ele=>!c.includes(JSON.stringify(ele)))

console.log(p)

answered Dec 27, 2018 at 5:38

Manoj

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