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Count vowels

Write a function countVowels(str), which takes a string str as an input. This function should return the total number of vowels in str.

Instructions

• Return 0 if str has no vowels.
• Assume that str may contain any alphanumeric characters.

Example test cases

countVowels("Hello world!"); // Output: 3
countVowels("This is a test"); // Output: 4
countVowels("No vowels here"); // Output: 0