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TypeScript vs JavaScript - Comparing the Key Differences

In this tutorial, we will compare TypeScript and JavaScript, two popular programming languages for building web applications. We will discuss their key differences, and how TypeScript's features can benefit developers working on modern, large-scale projects.

What is JavaScript?

JavaScript is a widely-used, dynamic programming language, primarily used for creating interactive web applications. It is supported by all modern web browsers and is a core technology of the World Wide Web, alongside HTML and CSS.

What is TypeScript?

As mentioned in the previous tutorial, TypeScript is a statically-typed superset of JavaScript developed by Microsoft. It adds optional type annotations to the language, which can help you catch errors during development and improve the overall maintainability and scalability of your code.

Key Differences

Let's explore the key differences between TypeScript and JavaScript:

1. Type System

JavaScript: JavaScript is a dynamically-typed language, which means that variable types are determined at runtime. This can lead to unexpected behavior and runtime errors if incorrect types are used.

TypeScript: TypeScript introduces an optional static type system that allows you to define the types of variables, function parameters, and return values. This helps catch type-related errors at compile time, reducing the number of runtime errors.

2. Tooling and Development Experience

JavaScript: While modern code editors offer some level of autocompletion and syntax checking for JavaScript, the lack of static types can limit the effectiveness of these features.

TypeScript: TypeScript's type system enables better code editor support, providing more accurate autocompletion, navigation, and refactoring tools. This can improve the overall development experience and productivity.

3. Code Maintainability

JavaScript: In large JavaScript codebases, it can be difficult to understand and maintain the code due to the lack of type information.

TypeScript: TypeScript's type system makes it easier to understand the structure and intent of the code, leading to better maintainability and scalability, especially in large projects.

4. Language Features

JavaScript: JavaScript has been evolving over the years with the introduction of new language features through ECMAScript standards. However, some features may not be available in all browsers, requiring polyfills or transpilation for compatibility.

TypeScript: TypeScript includes all the latest JavaScript features and adds additional functionality, such as interfaces, decorators, and namespaces. When TypeScript is transpiled, it can target different JavaScript versions, ensuring compatibility with various environments.

Sample Code Comparison

Let's compare JavaScript and TypeScript code to highlight their differences:

// JavaScript code
function add(a, b) {
return a + b;

var result = add(1, 2);
console.log(result); // Output: 3
// TypeScript code
function add(a: number, b: number): number {
return a + b;

let result: number = add(1, 2);
console.log(result); // Output: 3

In the TypeScript code, you can see type annotations for the function parameters, return value, and the result variable. These annotations help catch type-related errors and provide better tooling support.


Both TypeScript and JavaScript have their own advantages and use cases. TypeScript offers numerous benefits, such as improved type safety, better tooling, and easier maintainability, making it an excellent choice for large-scale projects. On the other hand, JavaScript is more suitable for smaller projects or when you need to support older browsers that might not be compatible with the latest TypeScript features.

In conclusion, understanding the key differences between TypeScript and JavaScript can help you make an informed decision about which language to use for your projects. By leveraging TypeScript's powerful features, you can build modern, robust, and maintainable web applications.