Hello, checkiomates🐱‍👤!

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This week, we look at new development tools, starting with the JS/TS Modernizer preview from Microsoft for updating legacy code. We then dive into the fun and challenge of implementing 2D physics using only JavaScript, and explore the latest and greatest features with the CSS Wrapped 2025 recap. Our mission challenges your string manipulation skills by asking you to count the vowels in a given text, case-insensitively.

💡TIP

On Easy difficulty, each of the few starting stations is dedicated to a distinct data type.
If you want to discover all CheckiO features, visit our tutorial. It's a longread, but it's worth it!

🏁MISSION

Count Vowels by freeman_lex -

This function should take a string as an input and return the count of vowels (a, e, i, o, u) in the string. The function should be case-insensitive.

assert.strictEqual(countVowels("hello"), 2);
assert.strictEqual(countVowels("openai"), 4);
assert.strictEqual(countVowels("typescript"), 2);

📖ARTICLES

Announcing the JavaScript/TypeScript Modernizer for VS Code -

Microsoft has unveiled a tool that analyzes a project and suggests an upgrade plan for both syntax and dependencies.

Golfing a 2D physics engine in JS -

A lovely, and rather old-school style post about building a simple physics engine from scratch in JavaScript then golfing it down to just 2KB of source

Chrome team's CSS Wrapped 2025 -

The Chrome DevRel team will guide you through 22 CSS and UI features that landed on the Web Platform, fresh from the kiln.

👩‍💻CODE SHOT

What do you think the following code does?

function checkio(arr: string[]): string {
  return arr.reduce(
    (a, b) => {
      let c = 0;
      while (c < a.length && c < b.length && a[c] == b[c]) ++c;
      return a.slice(0, c);
    }
  );
}

🙌 Thanks for your attention! Hope to meet you at CheckiO, as well as at our Instagram and Twitter! We are really interested in your thoughts! Please, leave a comment below! ⤵