✨ Add NN function

api.ts

@@ -66,6 +66,7 @@ const api: Api = {
   lt: ['ramda', 'lodash'],
   lte: ['ramda', 'lodash'],
   not: LAMBDAS,
+  NN: {},
   or: LAMBDAS,
   prepend: LAMBDAS,
   product: LAMBDAS,

mod.ts

@@ -46,6 +46,7 @@ export { lt } from './src/lt.ts'
 export { lte } from './src/lte.ts'
 export { map } from './src/map.ts'
 export { multiply } from './src/multiply.ts'
+export { NN } from './src/NN.ts'
 export { not } from './src/not.ts'
 export { or } from './src/or.ts'
 export { prepend } from './src/prepend.ts'

src/NN.ts

@@ -0,0 +1,35 @@
+// Copyright 2021-present the Fonction authors. All rights reserved. MIT license.
+import { Falsy } from './types/index.ts'
+/**
+ * Abbreviation for Not Not. Returns the `!!` of its argument.
+ *
+ * @param val - Input any value
+ * @returns The result of `!!val`
+ *
+ * @remarks
+ * The Definition of Falsy
+ * - `''`
+ * - `false`
+ * - `0`
+ * - `NaN`
+ * - `undefined`
+ * - `null`
+ *
+ * @example
+ * ```ts
+ * NN('') // false
+ * NN(false) // false
+ * NN(0) // false
+ * NN(NaN) // false
+ * NN(undefined) // false
+ * NN(null) // false
+ *
+ * NN({}) // true
+ * NN([]) // true
+ * ```
+ *
+ * @public
+ */
+const NN = <T>(val: T): T extends Falsy ? false : boolean =>
+  !!val as T extends Falsy ? false : boolean
+export { NN }

test/NN.test.ts

@@ -0,0 +1,40 @@
+// Copyright 2021-present the Fonction authors. All rights reserved. MIT license.
+import { assertEquals } from '../deps.ts'
+import { NN } from '../src/NN.ts'
+import { assertEqual } from './asserts.ts'
+
+Deno.test('NN', () => {
+  const table: [unknown, boolean][] = [
+    ['', false],
+    [undefined, false],
+    [null, false],
+    [0, false],
+    [NaN, false],
+    [false, false],
+    [[], true],
+    [{}, true],
+    ['hello', true],
+    [Infinity, true],
+    [1, true],
+    [-1, true],
+    [true, true]
+  ]
+
+  table.forEach(([val, expected]) => {
+    assertEquals(NN(val), expected, `NN(${val}) -> ${expected}`)
+  })
+
+  assertEqual<false>(NN('' as const))
+  assertEqual<false>(NN(0 as const))
+  assertEqual<false>(NN(false as const))
+  assertEqual<false>(NN(undefined))
+  assertEqual<false>(NN(null))
+  assertEqual<boolean>(NN(String))
+  assertEqual<boolean>(NN(Number))
+  assertEqual<boolean>(NN(NaN))
+  assertEqual<boolean>(NN(BigInt))
+  assertEqual<boolean>(NN(Symbol))
+  assertEqual<boolean>(NN(Date))
+  assertEqual<boolean>(NN(Object))
+  assertEqual<boolean>(NN(Array))
+})