merge: count Vowels (#864)

String/CountVowels.js

@@ -0,0 +1,25 @@
+/**
+ * @function countVowels
+ * @description Given a string of words or phrases, count the number of vowels.
+ * @param {String} url - The input string
+ * @return {Number} count
+ * @example countVowels("ABCDE") => 2
+ * @example countVowels("Hello") => 2
+ */
+
+const countVowels = (str) => {
+  if (typeof str !== 'string') {
+    throw new TypeError('Input should be a string')
+  }
+  const vowels = new Set(['a', 'e', 'i', 'o', 'u'])
+  let count = 0
+  for (let i = 0; i < str.length; i++) {
+    const char = str[i].toLowerCase()
+    if (vowels.has(char)) {
+      count++
+    }
+  }
+  return count
+}
+
+export { countVowels }