write function getOrdinalNumber()

Author: XiaoQuark

Sprint-3/2-practice-tdd/get-ordinal-number.js

@@ -1,5 +1,12 @@
 function getOrdinalNumber(num) {
-  return "1st";
+  const lastTwoDigits = num % 100;
+  if (lastTwoDigits === 11 || lastTwoDigits === 12 || lastTwoDigits === 13)
+    return `${num}th`;
+  const lastDigit = num % 10;
+  if (lastDigit === 1) return `${num}st`;
+  if (lastDigit === 2) return `${num}nd`;
+  if (lastDigit === 3) return `${num}rd`;
+  return `${num}th`;
 }
 
 module.exports = getOrdinalNumber;