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

Question

Hi I have an array of objects. Each object has array of objects. I need to find duplicates of (inner) objects what has the same value in a specific property. I made up to cr

Answer 1

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.