🐛 Fix types of length function

src/length.ts

@@ -1,20 +1,19 @@
 // Copyright 2021-present the Fonction authors. All rights reserved. MIT license.
 /**
- * Returns the number of elements in the array or string length.
+ * Returns length property.
  *
- * @param val - `string` or any `array`
+ * @param val - Value with length property
  * @returns The result of `val.length`
  *
  * @example
  * ```ts
  * length('hello') // 5
  * length(['hello', 'world', 1]) // 3
+ * length({length: 5, text: 'hello'}) // 5
  * ```
  *
- * @category `Array` `String`
- *
  * @public
  */
-const length = <T extends unknown[] | string>(val: T): T['length'] => val.length
+const length = <T extends { length: number }>(val: T): T['length'] => val.length
 
 export { length }

test/length.test.ts

@@ -1,9 +1,10 @@
 // Copyright 2021-present the Fonction authors. All rights reserved. MIT license.
 import { assertEquals } from '../dev_deps.ts'
 import { length } from '../src/length.ts'
+import { assertEqual } from './asserts.ts'
 
 Deno.test('length', () => {
-  const table: [unknown[] | string, number][] = [
+  const table: [{ length: number } | string, number][] = [
     ['', 0],
     [' ', 1],
     ['  ', 2],
@@ -13,10 +14,16 @@ Deno.test('length', () => {
     [[], 0],
     [[''], 1],
     [['', 0], 2],
-    [['', 0, '1'], 3]
+    [['', 0, '1'], 3],
+    [{ length: 3 }, 3]
   ]
 
   table.forEach(([val, expected]) => {
     assertEquals(length(val), expected, `length(${val}) -> ${expected}`)
   })
+
+  assertEqual<number>(length(''))
+  assertEqual<number>(length([]))
+  assertEqual<number>(length({ length: 1 }))
+  assertEqual<1>(length({ length: 1 } as const))
 })