Merge 1afd7b6 into 5cb1dfc

src/getTruthyKeys.ts

@@ -8,23 +8,22 @@ export default getTruthyKeys
  * @param collection Collection to iterate over.
  * @param parseKeyFunction Function invoked per iteration. This
  * function takes as parameter a key of a truthy value. The value it returns
- * will be used in resulting list. Note that if this function returns a falsy
- * value value, the key won't be present in resulting collection.
- * @returns New list with just the keys of truthy entries, for which
- * `parseKeyFunction` returned a truthy value.
+ * will be used in resulting list.
+ * @returns New list with just the keys of truthy entries.
  */
 function getTruthyKeys<T extends object, TResult>(
   collection: T | null | undefined,
   parseKeyFunction?: (key: string) => TResult
 ): (string | TResult)[] {
   const isFunction = _.isFunction(parseKeyFunction)
 
-  const mappedCollection = _.map(collection, function (value, key) {
-    if (!value) return false
-    return parseKeyFunction && isFunction ? parseKeyFunction(key) : key
-  })
-
-  return _.filter(mappedCollection) as (string | TResult)[] // Casting needed to remove `false`
+  return _.reduce(collection, function (acc: (string | TResult)[], value, key) {
+    if (value) {
+      const parsedKey = parseKeyFunction && isFunction ? parseKeyFunction(key) : key
+      acc.push(parsedKey)
+    }
+    return acc
+  }, [])
 }
 
 declare module 'lodash' {

test/unit/getTruthyKeys.spec.ts

@@ -15,11 +15,13 @@ describe('getTruthyKeys', function () {
       i: 1,
       j: { a: null },
       k: ['a'],
-      l: 'b'
+      l: 'b',
+      '': true,
+      false: true
     }
 
     const truthyKeys = getTruthyKeys(object)
-    const expectedTruthyKeys = ['a', 'f', 'g', 'i', 'j', 'k', 'l']
+    const expectedTruthyKeys = ['a', 'f', 'g', 'i', 'j', 'k', 'l', '', 'false']
 
     expect(truthyKeys).to.include.members(expectedTruthyKeys)
     expect(expectedTruthyKeys).to.include.members(truthyKeys)