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Sreeju S
Sreeju S

Posted on • Updated on

TypeScript vs JavaScript - What's the difference?

JavaScript and TypeScript although sharing a common syntax and purpose, they have significant variations in their essential functionality. While TypeScript adds capabilities like static typing to JavaScript, it is still fundamentally a superset of JavaScript. Let's take a closer look at the fundamental differences between TypeScript and JavaScript.

When comparing TypeScript to JavaScript, it's important to remember that most of the proper JavaScript code is valid TypeScript but not all. TypeScript may be thought of as a superset of JavaScript.

To say it simply:

JavaScript + more features = TypeScript

By analogy, if a JavaScript (.js) file is saved with a TypeScript (.ts) extension, it will compile and execute correctly. However, this does not imply that TypeScript and JavaScript are the same language.

Type System:

JavaScript: Dynamically Typed

  • In JavaScript, variables are dynamically typed, meaning the type of a variable is determined at runtime.
  • Example:
  let x = 10; // x is initially a number
  x = 'Hello'; // Later, x can be assigned a string
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TypeScript: Statically Typed

  • TypeScript, on the other hand, supports static typing, allowing explicit type declarations.
  • Example:
  let x: number = 10; // x is explicitly declared as a number
  // x = 'Hello'; // This would result in a TypeScript error as x is expected to be a number
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Tooling Support:

JavaScript: Basic Tooling

  • JavaScript has basic tooling support compared to TypeScript.
  • Developers often use various libraries and tools for development but may lack robust IDE support.

TypeScript: Advanced Tooling with IDE Support

  • TypeScript offers advanced tooling capabilities with extensive support in Integrated Development Environments (IDEs) like Visual Studio Code.
  • IDEs provide features like auto-completion, error checking, and refactoring support, enhancing the development experience.


JavaScript: Interpreted Directly by Browsers

  • JavaScript code is interpreted directly by browsers without the need for compilation.

TypeScript: Requires Compilation

  • TypeScript requires compilation into JavaScript before execution, using tools like the TypeScript compiler (tsc).

Error Detection:

JavaScript: Runtime Errors Possible

  • In JavaScript, errors may occur at runtime, making it challenging to catch all potential issues during development.

TypeScript: Early Error Detection at Compile-Time

  • TypeScript performs static type checking during compilation, enabling early detection of errors before the code is executed.

Extensions, Compatibility, Adoption, and More:

  • JavaScript files use the .js extension, while TypeScript files use .ts.
  • All JavaScript code is valid TypeScript, as TypeScript is a superset of JavaScript.
  • JavaScript has wider adoption, while TypeScript is increasingly gaining popularity, especially in larger projects.
  • TypeScript introduces additional features like interfaces, enums, generics, and more, offering enhanced capabilities over traditional JavaScript.
  • The learning curve for TypeScript might be steeper due to its added features, especially for developers transitioning from JavaScript.

JavaScript remains a fundamental language for web development, TypeScript emerges as a powerful alternative offering static typing, early error detection, and advanced tooling support. Understanding the differences between these languages can assist developers in choosing the right tool for their projects based on specific requirements and preferences.

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Top comments (1)

jonrandy profile image
Jon Randy 🎖️

All JavaScript code is valid TypeScript, as TypeScript is a superset of JavaScript.

Strictly it is a syntactic superset, as some identical code will not do the same thing in TS as it would in JS.