lodash - "Count where" in a collection

Question

Using lodash, what would be a good way to count the number of objects in a collection conditionally? Say I wanted to count the number of objects where

a < 4

in the following collection

[{a : 1}, {a : 2}, {a : 3}, {a : 4}, {a : 5}, {a : 6}]

question from:https://stackoverflow.com/questions/35562307/count-where-in-a-collection

Answer 1

You can use sumBy for this:

const count = _.sumBy(
  objects,
  ({ a }) => Number(a < 4)
);

---

Alternatively, you can write it with lodash/fp:

const count = _.sumBy(_.flow(_.get('a'), _.lt(4), Number), objects);