| JNTech

JavaScript vs TypeScript

Published on 10 Nov 2026 2 min read React

React Fundamentals

JavaScript vs TypeScript

JavaScript	TypeScript
`.js` / `.jsx` files	`.ts` / `.tsx` files
Dynamically typed	Statically typed
Types are not required	Types can be explicitly defined
Easier to start	More structured
Errors may appear at runtime	Many errors are caught during development
Good for small projects	Excellent for large applications

function User({ name, age }) {
    return <h2>{name} - {age}</h2>;
}

You don't specify what type name or age should be.

You could accidentally do:

<User name={100} age="twenty" />

JavaScript generally won't complain about these types during development.

interface UserProps {
    name: string;
    age: number;
}

function User({ name, age }: UserProps) {
    return <h2>{name} - {age}</h2>;
}

Now TypeScript knows:

name → string
age  → number

So this produces a type error:

<User name={100} age="twenty" />

because:

100       → number ❌
"twenty"  → string ❌

With JavaScript:

src/
├── App.jsx
├── main.jsx
└── components/
    └── Header.jsx

With TypeScript:

src/
├── App.tsx
├── main.tsx
└── components/
    └── Header.tsx

.tsx is used when the file contains TypeScript + JSX.

For your situation, I recommend:

React + TypeScript

because you're coming from a C#/.NET background. TypeScript's strong typing will feel familiar:

string name;
int age;

similar to:

let name: string;
let age: number;

For a React 19 + ASP.NET Core Web API project, a very good stack is:

React 19
   +
TypeScript
   +
Vite
   +
Axios
   +
ASP.NET Core Web API