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Challenge: Unit Test a Vowels Counter Function

Explore how to write unit tests for a JavaScript vowels counter function using Jest. Understand regex usage for matching vowels and practice verifying expected outcomes to ensure function correctness.

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Challenge overview

Javascript (babel-node)
const vowels = (str) => {
  const matches = str.match(/[aeiou]/gi);
  return matches ? matches.length : 0;
};

Let’s explain the code written in the example above:

  • In line 1, we have a vowels function that takes in one parameter, str, which is a word passed into the function as a JavaScript string to test.

  • In line 2, we use a regular expression to find all the matches of vowels in the string (i.e., /aeiou/gi ...