feat(select): let condition be undefined (#9)

* feat(select): let `condition` be undefined

* test: select without a condition callback

Co-authored-by: Adam C Hamlin <[email protected]>

src/array/select.ts

@@ -8,12 +8,13 @@
 export const select = <T, K>(
   array: readonly T[],
   mapper: (item: T, index: number) => K,
-  condition: (item: T, index: number) => boolean
+  condition?: (item: T, index: number) => boolean
 ) => {
   if (!array) return []
+  let mapped: K
   return array.reduce((acc, item, index) => {
-    if (!condition(item, index)) return acc
-    acc.push(mapper(item, index))
+    if (condition) condition(item, index) && acc.push(mapper(item, index))
+    else (mapped = mapper(item, index)) != null && acc.push(mapped)
     return acc
   }, [] as K[])
 }

src/array/tests/select.test.ts

@@ -52,4 +52,9 @@ describe('select function', () => {
     )
     expect(result).toEqual(['c2', 'd3'])
   })
+  test('works without a condition callback', () => {
+    const list = [{ a: 1 }, { b: 2 }, { a: 3 }, { a: null }, { a: undefined }]
+    const result = _.select(list, obj => obj.a)
+    expect(result).toEqual([1, 3])
+  })
 })