Shortest way to find duplicates in array of arrays of objects by property

Question

Hi I have an array of objects. Each object has an array of objects. I need to find duplicates of (inner) objects that have the same value in a specific property. I made up to create a loop inside the loop and use include.
Is there a shorter way of doing this?

    // Verify that there are no duplicate device names.
    const streamItemNames = [];
    for (let i = 0, length1 = validateStreamItemsResults.streamWebSockets; i < length1; i++) {

        const streamItems = validateStreamItemsResults.streamWebSockets[i].streamItems;

        for (let y = 0, length2 = streamItems.length; y < length2; y++) {

            const streamItem = streamItems[i];
            const streamItemNameLower = streamItem.streamItemName.trim().toLowerCase();

            if (streamItemNames.includes(streamItemNameLower)) {
                validateStreamItemsResults.errorMessage = `Duplicate stream items found with the name: ${streamItemNameLower}`;
                return validateStreamItemsResults;
            } else {
                streamItemNames.push(streamItemNameLower);
            }
        }
    }

UPDATE:
The structure of the objects is the following, for example:
(I need to determine with true or false if there are duplicates "streamItemName" - In the case of this example - true).

const childArray1 = [ { streamItemName: 'Name1' }, { streamItemName: 'Name2' }, { streamItemName: 'Name3' }, { streamItemName: 'Name4' }];
const childArray2 = [ { streamItemName: 'Name5' }, { streamItemName: 'Name6' }, { streamItemName: 'Name7' }, { streamItemName: 'Name1' }];
const parentArray = [childArray1, childArray2];

See stackoverflow.com/help/mcve. What do you mean by "shortest"? In bytes? — guest271314
– guest271314, Commented Feb 28, 2019 at 8:25

CertainPerformance · Accepted Answer · 2019-02-28 08:33:44Z

3

If you're looking for clearer, shorter code, you could use flatMap to extract every streamItemName into a single array, then use .find to find if there are any duplicates:

const streamItemNames = validateStreamItemsResults.streamWebSockets.flatMap(
  socket => socket.streamItems.map(
    item => item.streamItemName.trim().toLowerCase()
  )
);
const dupe = streamItemNames.find((name, i, arr) => arr.slice(i + 1).includes(name));
if (dupe) {
  validateStreamItemsResults.errorMessage = `Duplicate stream items found with the name: ${dupe}`;
  return validateStreamItemsResults;
}

If you don't need to know the duplicate name, you could make it shorter by making a Set and comparing its .size against the array's length.

answered Feb 28, 2019 at 8:33

CertainPerformance

373k55 gold badges354 silver badges359 bronze badges

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

3 Comments

soupy-norman Over a year ago

Since there might be more than one duplicate wouldn't Arrayprototype.filter() be more fitting? const dupes = streamItemNames.filter((name, i, arr) => arr.slice(i + 1).includes(name)); returning an array of duplicates.

CertainPerformance Over a year ago

From his code, it looks like OP only wants one duplicate. If he wanted an array instead of just one, then yes, better to .filter

soupy-norman Over a year ago

Huh. You are right. He makes it clear that he only need to know whether or not there are any duplicates - in the parenthesis of the updated statement.

Collectives™ on Stack Overflow

Shortest way to find duplicates in array of arrays of objects by property

1 Answer 1

3 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related