Using JavaScript to compare 2 arrays and create a new array of objects which does not contains the objects that match by id field

Question

I have two arrays of objects. I would like to use JavaScript to create a new array which does not contains object that match by id field.

First array

[{id: 1, name: "Jo"},{id: 2, name: "Pat"},{id: 3, name: "Mike"}]

Second array

[{id: 1, name: "Jo"},{id: 2, name: "Pat"},{id: 3, name: "Mike"}, {id: 4, name: "Mitch"}, {id: 5, name: "Karl"}]

should return this array

[{id: 4, name: "Mitch"}, {id: 5, name: "Karl"}]

Using lodash would be better if possible. Please note that the first array is always smaller or equal to the second one and can only contain objects that are in the second one.

So I tried the following...

let newArray = _.reject(secondArray, {'id': firstArray});

Without success, I need help with the syntax.

Many thanks for your time and help.

Much better :) what didn't work about your attempt? I know of a dirty way to solve this problem that uses native JS, but I'm not sure if it'd be what you're looking for — Nick Zuber
– Nick Zuber, Commented Mar 4, 2016 at 3:00
Yes I know, sorry about that. Please look at Hatchet's answer, short and sweet. — Gab
– Gab, Commented Mar 4, 2016 at 3:03

Hatchet · Accepted Answer · 2016-03-04 03:06:51Z

4

Short and sweet. (Assumes one holds the first array and two holds the second array)

var oneIDs = one.map(function (a) {return a.id});

var result = two.filter(function (a) {
    return oneIDs.indexOf(a.id) === -1;
});

Explanation:

First, get a lookup array of all the id's of the elements in the first array.

Second, get all the elements of the second array whose id's are not in the lookup array (oneIDs).

edited Mar 4, 2016 at 3:06

answered Mar 4, 2016 at 2:58

Hatchet

5,4161 gold badge35 silver badges43 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Using JavaScript to compare 2 arrays and create a new array of objects which does not contains the objects that match by id field

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related