Hello, checkiomates🐱‍👤!

This week in JavaScript, we explore how to write more reliable code using optional chaining, delve into the intricacies of working with dates, and learn about JavaScript from "JavaScript: The Documentary". To wrap it up, we present a mission to find and create the word "CheckIO" within a given string using the fewest possible replacements.

💡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

Tricky String by freeman_lex -

You are given a string. Somewhere in that text a word "CheckIO" has hidden. Your task is to find a place where word is hiding and make the minimum number of replacements to get it. Let's proceed with an example: for a string "xheckIO" you should replace only one symbol ("x" to "C") to get a desired word, on the other hand we can try to find it in more complex string: "CheckzzVSCheckIz", right answer here will be a string "CheckzzVSCheckIO" (only one replacemend has made "z" to "O").

assert.strictEqual(trickyString("checkIO"), "CheckIO");
assert.strictEqual(trickyString("zcheckzz"), "zCheckIO");
assert.strictEqual(trickyString("SoManyChoicesHere"), "SoManyCheckIOHere");

📖ARTICLES

Write more reliable JavaScript with optional chaining -

Optional chaining is a game-changer for writing safer, cleaner JavaScript. It reduces boilerplate, improves readability, and helps you avoid those pesky runtime errors when accessing deeply nested properties.

Why are 2025/05/28 and 2025-05-28 different days in JavaScript? -

An interesting ‘Wat’-like moment in just the first few lines of this post, which Brandon decided to dig into and explain.

Modern Performance Debugging in Chrome DevTools -

Paul shares a look at the reimagined Chrome DevTools Performance panel, showing off new features, how they work, and how to use them to make performance gains.

👩‍💻CODE SHOT

What do you think the following code does?

function ????????????(text: string): boolean {
    return text.split(" ").map(Number).join("").indexOf("NaNNaNNaN") !=-1
}

🙌 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! ⤵