add snake-case

3 years ago · 0a7205cd60
parent e4a2801c98
commit 0a7205cd60
1 changed files with 19 additions and 0 deletions
--- a/19
+++ b/19
@ -0,0 +1,19 @@
+import type { Equal, Expect } from '@type-challenges/utils'
+
+type cases = [
+  Expect<Equal<SnakeCase<'hello'>, 'hello'>>,
+  Expect<Equal<SnakeCase<'userName'>, 'user_name'>>,
+  Expect<Equal<SnakeCase<'getElementById'>, 'get_element_by_id'>>,
+  Expect<Equal<SnakeCase<'getElementById' | 'getElementByClassNames'>, 'get_element_by_id' | 'get_element_by_class_names'>>,
+]
+
+type SnakeCase<
+  T extends string,
+  Acc extends string = '',
+> =
+T extends `${infer Head}${infer Tail}`
+  ? Head extends Lowercase<Head>
+    ? SnakeCase<Tail, `${Acc}${Head}`>
+    : SnakeCase<Tail, `${Acc}_${Lowercase<Head>}`>
+  : Acc
+;