What is a difference between TypeScript and JavaScript?

TypeScript and JavaScript are both programming languages that are used to build web applications, but there are some key differences between them:

1. TypeScript is a statically typed language, while JavaScript is dynamically typed: This means that in TypeScript, you must declare the type of a variable when you declare it, whereas in JavaScript, the type of a variable can change at runtime.
2. TypeScript has features from the latest versions of ECMAScript: TypeScript is a superset of JavaScript and includes features from the latest versions of ECMAScript, the standard that defines JavaScript. This means that you can write code that uses these new features in TypeScript, even if they are not yet widely supported in browsers.
3. TypeScript has optional type annotations: TypeScript allows you to specify the type of a variable, function return value, or function argument. This can make your code easier to understand and maintain, because the type information can be used by the TypeScript compiler to catch type errors at compile-time, rather than at runtime.
4. TypeScript has a stronger focus on class-based object-oriented programming: TypeScript has a stronger focus on class-based object-oriented programming, whereas JavaScript is more procedural in nature. TypeScript supports features such as classes, interfaces, and decorators that are not available in JavaScript.
5. TypeScript requires a compiler: TypeScript code must be compiled into JavaScript before it can be run in a browser or on a server. This adds an extra step to the development process, but it also makes it easier to catch type errors and other issues before they become problems in the compiled code.

In summary, TypeScript provides additional features and a stricter type system on top of JavaScript, making it a good choice for larger, more complex applications where maintainability is a concern. JavaScript, on the other hand, is a lighter-weight language that is easier to get started with, but may require more careful testing and debugging as the codebase grows.