Add randomArrayElem

docs/modules/Random.ts.md

@@ -14,6 +14,7 @@ Added in v2.0.0
 
 - [utils](#utils)
   - [random](#random)
+  - [randomArrayElem](#randomarrayelem)
   - [randomBool](#randombool)
   - [randomElem](#randomelem)
   - [randomInt](#randomint)
@@ -36,6 +37,18 @@ export declare const random: IO<number>
 
 Added in v2.0.0
 
+## randomArrayElem
+
+Returns a random element of a `ReadonlyArray`.
+
+**Signature**
+
+```ts
+export declare const randomArrayElem: <A>(as: readonly A[]) => IOOption<A>
+```
+
+Added in v2.13.2
+
 ## randomBool
 
 Returns a random boolean value with an equal chance of being `true` or `false`

src/Random.ts

@@ -1,8 +1,10 @@
 /**
  * @since 2.0.0
  */
+import { flow, pipe } from './function'
 import { IO, map } from './IO'
-import { pipe } from './function'
+import { fromIO, IOOption, none } from './IOOption'
+import { match } from './ReadonlyArray'
 import { ReadonlyNonEmptyArray } from './ReadonlyNonEmptyArray'
 
 /**
@@ -60,3 +62,14 @@ export const randomElem = <A>(as: ReadonlyNonEmptyArray<A>): IO<A> =>
     randomInt(0, as.length - 1),
     map((i) => as[i])
   )
+
+/**
+ * Returns a random element of a `ReadonlyArray`.
+ *
+ * @since 2.13.2
+ */
+export const randomArrayElem = <A>(as: ReadonlyArray<A>): IOOption<A> =>
+  pipe(
+    as,
+    match(() => none, flow(randomElem, fromIO))
+  )

test/Random.ts

@@ -1,5 +1,6 @@
-import * as U from './util'
+import { isSome, none } from '../src/Option'
 import * as _ from '../src/Random'
+import * as U from './util'
 
 describe('Random', () => {
   it('random', () => {
@@ -33,4 +34,10 @@ describe('Random', () => {
     const e = _.randomElem([1, 2, 3])()
     U.deepStrictEqual(e >= 1 && e <= 3, true)
   })
+
+  it('randomArrayElem', () => {
+    const eOption = _.randomArrayElem([1, 2, 3])()
+    U.deepStrictEqual(_.randomArrayElem([])(), none)
+    U.deepStrictEqual(isSome(eOption) && eOption.value >= 1 && eOption.value <= 3, true)
+  })
 })