JavaScript reduce returns null if array is empty

Question

I need the count of my objects in the array based on their type. I don't know what I'm missing here, but this is what I do:

myCounts = (myArray || []).reduce(function _countMembersByType(counts, member) {
  return counts[member.type === productType.GROUP ? 'groupCount' : 'individualCount']++;
}, {groupCount: 0 , individualCount: 0});

When myArray has members, myCounts will be null. Otherwise, it will be an object as myCounts: {"groupCount":0,"individualCount":0} as I would expect.

I'm new to JS and would appreciate any help!

You mean When myArray does NOT have members

mplungjan
– mplungjan

2016-06-10 13:00:55 +00:00
Commented Jun 10, 2016 at 13:00 — mplungjan
– mplungjan, Commented Jun 10, 2016 at 13:00

ste2425 · Accepted Answer · 2016-06-10 13:01:06Z

2

Your returning the result of plus 1'ing, so in the next iteration, previous or counts will be a number not your base object.

You need to return the whole object.

myCounts = (myArray || []).reduce(function _countMembersByType(counts, member) {
  counts[member.type === productType.GROUP ? 'groupCount' : 'individualCount']++;
  return counts;
}, {
  groupCount: 0,
  individualCount: 0
});

fiddle

answered Jun 10, 2016 at 13:01

ste2425

4,8473 gold badges26 silver badges39 bronze badges

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

1 Comment

Yalda Over a year ago

Oh I see! Dumb mistake! Thanks :)

Collectives™ on Stack Overflow

JavaScript reduce returns null if array is empty

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related