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Advanced and Creative TypeScript Techniques for Professionals

Shafayet Hossain on December 15, 2024

TypeScript has established itself as the go-to tool for building scalable, maintainable, and efficient applications. Its type system is not only ro...

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eshimischi • Dec 15

github.com/ts-essentials/ts-essent...

Viswanath R • Dec 16

Great article

Shafayet Hossain • Dec 16

Thanks for the kind words🖤

makkentoshh {{☕}} • Dec 16

Amazing!

Shafayet Hossain • Dec 16

Thanks for checking it out😊🖤

Ameni Ben Saada • Dec 16

Thanks for sharing

Shafayet Hossain • Dec 16

No problem at all. Hope it adds value!😊😊

Adam • Dec 15

Great series!

Shafayet Hossain • Dec 16

You're welcome! Glad you found it useful.😊🖤

Serhiy • Dec 17

Great! Thanks!

Shafayet Hossain • Dec 17

Thanks for reading and appreciating the effort😊

Nozibul Islam • Dec 15

thanks for sharing a great article.

Shafayet Hossain • Dec 16

Thanks for taking the time to read it!🖤

Clark Allison LLP • Dec 17

Good!

Shafayet Hossain • Dec 17

Thanks, appreciate the kind words!🖤

Minhaz Halim (Zim) • Dec 17

Very creative and useful article. Thanks bro....

Shafayet Hossain • Dec 17

I'm glad it was useful to you. That's what I aimed for!!🖤

Juan Labrada • Dec 17

Nice article!! I have a question. I'm still figuring out the usefullness of Type Guards, which in principle seems fine, but in practice it seems awkward. The "typeof" operator have been out in the field in many languages and the examples I have seen both in your article and in the TypeScript documentation doesn't explain the need for that Type Guard.
For example: the isString function if the type guard ensures the value is string then why not just return true? At the same time it defeats the purpose to have a function that always returns true. And what would be the behaviour if I call the function with a number?
Just for the sake of understanding I created a test which worked the same with the type guard and without it, so, I can't spot the value of having such syntax.

Shafayet Hossain • Dec 17 • Edited

It's a great question, Juan! Type Guards like isString aren't just about returning true or false they narrow down the type of a variable, enabling TypeScript to provide better type-checking and autocomplete support.

For example, in your isString test:

if (isString(value)) {
  console.log(value.toUpperCase()); // Safe: 'value' is now inferred as 'string'
}

Without the guard, TypeScript wouldn't know value is a string, and toUpperCase() would throw an error for non-strings.
This mechanism shines when working with unknown or any types, union types (string | number), or complex objects. Guards ensure safety while avoiding redundant casting.
Your tests likely work because you're manually ensuring the values match expected types. In dynamic code, where inputs aren't predictable, Type Guards save the day. They're less about "returning true" and more about refining types to avoid runtime errors.
Let me know if you have any other questions...😊