Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

JavaScript React by Example Building the Application Creating the Counter

Posted by Anthony Albertorio
Anthony Albertorio
22,624 Points

Why not use .filter() instead of .reduce() for getAttendingGuests()?

Why not use simpler code? 

  getAttendingGuests = () =>
    this.state.guests.filter( guest => guest.isConfirmed).length;

1 Answer

Steven Parker
Steven Parker
229,644 Points
Steven Parker
Steven Parker
229,644 Points

The code might be a bit more compact, but I'd expect that the "reduce" version is more efficient. Try them both in a benchmarking tool and see!.

Anthony Albertorio
Anthony Albertorio
22,624 Points

How would I be able to do that? Any suggestions?

Steven Parker
Steven Parker
229,644 Points
Steven Parker
Steven Parker
229,644 Points

There are a number of online benchmarking and comparison tools around. I was curious to see if my guess was correct so I tried it myself over at JS Bench.

It said the original (reduce) version is five times faster than doing it with filter.