Introduction to TypeScript: Why Use TypeScript Over JavaScript?

Introduction

You know those red squiggly lines in your code editor? The ones that show up when you misspell a word or forget a semicolon? Most of the time, we appreciate them, they catch our mistakes before we embarrass ourselves.

But what if your editor could catch logic mistakes too? What if it could warn you before you try to access a property on undefined, or pass the wrong type of data to a function?

That's exactly what TypeScript does. And while those red squiggles might seem annoying at first, they're actually your best friend, preventing bugs from reaching your users and making your code more reliable.

Let's explore what TypeScript is, why it exists, and whether it's right for you.

What is TypeScript?

Here's the simplest way to think about TypeScript: it's JavaScript with types.

More precisely, TypeScript is a "superset" of JavaScript. This means every valid JavaScript program is also a valid TypeScript program. You can take any .js file, rename it to .ts, and it will work. TypeScript doesn't replace JavaScript—it extends it.

Here's a regular JavaScript function:

function greet(name) {
  return "Hello, " + name + "!";
}

greet("World"); // "Hello, World!"
greet(42); // "Hello, 42!" (probably not what we wanted)

And here's the same function in TypeScript:

function greet(name: string): string {
  return "Hello, " + name + "!";
}

greet("World"); // "Hello, World!"
greet(42); // Error: Argument of type 'number' is not assignable to parameter of type 'string'

The difference? We added : string to tell TypeScript what type of data we expect. Now TypeScript can catch the mistake before our code runs.

But here's the key insight: TypeScript doesn't run in browsers or Node.js. It compiles down to regular JavaScript. Think of it as a smart translator that checks your code for problems and then converts it to the JavaScript that actually runs.

This matters because you get all the development-time benefits of type checking without affecting what your users actually download and run. Your users get the same fast JavaScript they always have, but you wrote it with the safety net of types. It's like having a careful editor review your writing before publishing, but the published version is just your original words.

The Core Problem TypeScript Solves

Think about when you usually discover bugs in your JavaScript code.

If you're like most developers, it's often when:

• You're testing in the browser and something crashes
• A user reports an error
• You're debugging at 2 AM wondering why undefined is not a function

These scenarios have something in common: you're discovering problems when your code is actually running in the browser or on the server, serving real users. This is called runtime. JavaScript traditionally only catches errors at runtime, when it's too late and users are already affected.

TypeScript catches many of these same errors at compile time, while you're still writing and building your code, before anyone uses it.

Consider this common JavaScript scenario:

const user = getUser();
console.log(user.name.toUpperCase()); // Works fine... until getUser() returns null

In JavaScript, this will happily run until the day getUser() returns null, and then your app crashes with "Cannot read property 'toUpperCase' of null."

TypeScript catches this before your code ever runs:

const user = getUser(); // TypeScript knows this might return null
console.log(user.name.toUpperCase()); // Error: Object is possibly 'null'

The red squiggles force you to handle the case where user might be null:

const user = getUser();
if (user) {
  console.log(user.name.toUpperCase()); // Now it's safe
}

This shift from runtime to compile-time error detection is TypeScript's superpower.

Key Benefits of TypeScript

1. Fewer Bugs in Production

Those "annoying" red squiggles in your editor? They're catching bugs that would otherwise reach your users. Every time TypeScript complains about a type mismatch, it's potentially saving you from a runtime error, a confused user, or a late-night debugging session.

2. Self-Documenting Code

Types serve as living documentation that can't get out of sync with your code. When you see:

function calculateTax(price: number, rate: number): number {
  return price * rate;
}

You immediately know what this function expects and what it returns. No need to dig through the implementation or guess based on variable names.

3. Better Developer Experience

With TypeScript, autocomplete actually works. When you type user. in JavaScript, your editor can only guess what might be available. With TypeScript, it knows exactly what properties exist on the user object because you've defined them. This means fewer trips to documentation and fewer typos that break your code in subtle ways.

This same type information that makes autocomplete work also transforms refactoring. In JavaScript, when you change a function signature or rename a property, you're essentially flying blind. You can search for text matches, but you don't know if you've found all the real usages or just coincidental matches.

TypeScript gives you certainty. It tracks every actual usage of your code across your entire project. When you make a change, TypeScript will tell you exactly what breaks and where. Instead of deploying and hoping, you get a complete list of what needs to be fixed.

4. Forces Better Architecture

Here's something interesting: TypeScript makes you think about your code structure upfront. When you have to define interfaces and types, you're essentially mapping out the relationships between different parts of your application.

This might feel like extra work initially, but it leads to more thoughtful, well-structured code. You're less likely to create tangled dependencies or unclear data flows.

The Learning Curve Reality

If you're reading this and thinking TypeScript sounds amazing, you're right. But you're probably also wondering what the catch is. Here it is: there's a learning curve. TypeScript will slow you down at first. You'll spend time fixing type errors that feel pointless. You'll find yourself thinking, "This worked perfectly fine in JavaScript!"

But here's what happens after a few weeks:

1. You start catching bugs before they happen
2. Refactoring becomes confident instead of scary
3. You write more robust code naturally
4. The red squiggles feel helpful, not annoying

The key insight is that TypeScript is training you to write better code. Those type errors aren't arbitrary obstacles—they're pointing out real potential problems in your logic.

Summary

TypeScript is JavaScript with a type system that catches errors at compile time instead of runtime. While it requires a learning investment upfront, it pays dividends in code reliability, developer experience, and maintainability—especially for team projects and large applications.

The question isn't whether TypeScript is "better" than JavaScript—they serve different needs. JavaScript is perfect for quick scripts and learning. TypeScript excels when code quality, team collaboration, and long-term maintenance matter.

Ready to give it a try? Let's start with installation and setup in the next article.