[5kyu][functionl-programming][math] A Chain adding function

https://www.codewars.com/kata/539a0e4d85e3425cb0000a88/solutions/typescript

We want to create a function that will add numbers together when called
in succession.

lib/cheinAddFun.ts

@@ -0,0 +1,12 @@
+// We want to create a function that will add numbers together when called in succession.
+
+export default function add(x: number): any {
+  const fn = (y: number) => add(x + y);
+  fn.valueOf = () => x;
+  return fn;
+}
+
+const seven = add(1)(2)(4);
+console.log(seven == 7, 'expect 7')
+
+console.log(+add(1)(2), 'expect 3')