implement "coolDown"-function w/ tests & update "froth" to accept extended Latin alphabets

Author: pr0fix

src/coolDown.ts

@@ -0,0 +1,20 @@
+export function coolDown(str: string): string | null {
+  if (typeof str !== "string") {
+    return null;
+  }
+
+  let i = 0;
+  let result = "";
+
+  while (str[i] !== undefined) {
+    result += String.fromCharCode(
+      (str.charCodeAt(i) > 64 && str.charCodeAt(i) < 91) ||
+        (str.charCodeAt(i) > 191 && str.charCodeAt(i) < 224)
+        ? str.charCodeAt(i) + 32
+        : str.charCodeAt(i)
+    );
+    i++;
+  }
+
+  return result;
+}

src/froth.ts

@@ -11,7 +11,7 @@
  * froth(123); // Returns null
  * ```
  */
-export function froth(str: string) {
+export function froth(str: string): string | null {
   if (typeof str !== "string") {
     return null;
   }
@@ -21,7 +21,8 @@ export function froth(str: string) {
 
   while (str[i] !== undefined) {
     result += String.fromCharCode(
-      str.charCodeAt(i) > 96 && str.charCodeAt(i) < 123
+      (str.charCodeAt(i) > 96 && str.charCodeAt(i) < 123) ||
+        (str.charCodeAt(i) > 223 && str.charCodeAt(i) < 256)
         ? str.charCodeAt(i) - 32
         : str.charCodeAt(i)
     );

src/hasMilk.ts

@@ -16,7 +16,7 @@
  * ```
  */
 
-export function hasMilk(str: string, word: string) {
+export function hasMilk(str: string, word: string): boolean | null {
   if (typeof str !== "string" || typeof word !== "string") {
     return null;
   }

src/index.ts

@@ -1,5 +1,6 @@
 export { brewLength } from "./brewLength";
 export { compareBeans } from "./compareBeans";
+export { coolDown } from "./coolDown";
 export { findFirstSip } from "./findFirstSip";
 export { findFlavor } from "./findFlavor";
 export { froth } from "./froth";

src/pourCoffee.ts

@@ -11,7 +11,7 @@
  * pourCoffee(123); // Returns null
  * ```
  */
-export function pourCoffee(str: string) {
+export function pourCoffee(str: string): string | null {
   if (typeof str !== "string") {
     return null;
   }

tests/coolDown.test.ts

@@ -0,0 +1,25 @@
+import { coolDown } from "../src/index";
+
+test("coolDown should return string in lowercase", () => {
+  expect(coolDown("COFFEE")).toBe("coffee");
+  expect(coolDown("cOfFeE")).toBe("coffee");
+});
+
+test("coolDown should return string with extended Latin alphabets in lowercase", () => {
+  expect(coolDown("ÄÖÅ")).toBe("äöå");
+});
+
+test("coolDown should not return a string containing uppercase letters", () => {
+  expect(coolDown("coffee")).not.toBe("COFFEE");
+  expect(coolDown("COFFEE")).not.toBe("COFFEE");
+  expect(coolDown("cOfFeE")).not.toBe("COFFEE");
+});
+
+test("coolDown should return null for non strings", () => {
+  expect(coolDown(0 as any)).toBeNull();
+  expect(coolDown(true as any)).toBeNull();
+  expect(coolDown({} as any)).toBeNull();
+  expect(coolDown([] as any)).toBeNull();
+  expect(coolDown(undefined as any)).toBeNull();
+  expect(coolDown(null as any)).toBeNull();
+});

tests/froth.test.ts

@@ -1,10 +1,14 @@
 import { froth } from "../src/index";
 
-test("froth to return string in uppercase", () => {
+test("froth should return string in uppercase", () => {
   expect(froth("coffee")).toBe("COFFEE");
   expect(froth("cOfFeE")).toBe("COFFEE");
 });
 
+test("froth should return string with extended Latin alphabets in uppercase", () => {
+  expect(froth("äöå")).toBe("ÄÖÅ");
+});
+
 test("froth should not return a string containing lowercase letters", () => {
   expect(froth("coffee")).not.toBe("coffee");
   expect(froth("COFFEE")).not.toBe("coffee");