description:

when using _.sumBy on an array of objects with boolean values, the result is a boolean when the array contains only one item

reproduction

run this code on https://playcode.io/lodash:

import _ from 'lodash';

const result = _.sumBy([{ bool: true }], 'bool');

console.log(_.VERSION);         // 4.17.21
console.log(result);            // expected: 1, actual: true
console.log(typeof result);     // expected: 'number', actual: 'boolean
console.log(result === true);   // expected: false, actual: true
console.log(result === 1);      // expected: true, actual: false

expected behaviour
lodash should coerce boolean values to numbers (true → 1, false → 0) consistently, even for single-item arrays.

notes
for quick fix replace

_.sumBy([{ bool: true }], 'bool')

with

_.filter([{ bool: true }], item => item.bool).length