Write tests and implement the function for Get Ordinal Number task

Author: ausiejute

practice-tdd/get-ordinal-number.js

@@ -1,3 +1,25 @@
 export function getOrdinalNumber(num) {
-  return "1st";
+  if (num === null || num === undefined || num === "" || num < 0) {
+    throw new Error("Invalid input!");
+  }
+
+  if (typeof num !== "number" || !isFinite(num)) {
+    throw new Error("Invalid input!");
+  }
+
+  const lastDigit = num % 10;
+  const lastTwoDigits = num % 100;
+
+  if (lastTwoDigits >= 11 && lastTwoDigits <= 13) {
+    return `${num}th`;
+  }
+
+  if (lastDigit === 1) {
+    return `${num}st`;
+  } else if (lastDigit === 2) {
+    return `${num}nd`;
+  } else if (lastDigit === 3) {
+    return `${num}rd`;
+  }
+  return `${num}th`;
 }

practice-tdd/get-ordinal-number.test.js

@@ -18,3 +18,29 @@ test("should append 'st' for numbers ending with 1, except those ending with 11"
   expect(getOrdinalNumber(21)).toEqual("21st");
   expect(getOrdinalNumber(131)).toEqual("131st");
 });
+
+test("should append 'nd' for numbers ending with 2, except those ending with 12", () => {
+  expect(getOrdinalNumber(2)).toEqual("2nd");
+  expect(getOrdinalNumber(32)).toEqual("32nd");
+  expect(getOrdinalNumber(102)).toEqual("102nd");
+});
+
+test("should append 'rd' for numbers ending with 3, except those ending with 13", () => {
+  expect(getOrdinalNumber(3)).toEqual("3rd");
+  expect(getOrdinalNumber(53)).toEqual("53rd");
+  expect(getOrdinalNumber(123)).toEqual("123rd");
+});
+
+test("should append 'th' for the rest of the numbers", () => {
+  expect(getOrdinalNumber(9)).toEqual("9th");
+  expect(getOrdinalNumber(20)).toEqual("20th");
+  expect(getOrdinalNumber(108)).toEqual("108th");
+});
+
+test("should throw an error if the input is invalid", () => {
+  expect(() => getOrdinalNumber("")).toThrow("Invalid input!");
+  expect(() => getOrdinalNumber("fifty two")).toThrow("Invalid input!");
+  expect(() => getOrdinalNumber(-3)).toThrow("Invalid input!");
+  expect(() => getOrdinalNumber(null)).toThrow("Invalid input!");
+  expect(() => getOrdinalNumber(undefined)).toThrow("Invalid input!");
+});