What is TypeScript?

TypeScript is a programming language designed by Anders Hejlsberg, the founder of the C# language. It is the result of an assessment of the JavaScript language, and what could be done to help developers when writing JavaScript. TypeScript includes a compiler which will transform code written in TypeScript into JavaScript. It's beauty is really in its simplicity. We can take existing JavaScript, add a few TypeScript keywords here and there, and transform our code into a strongly-typed, object-oriented, syntax-checked code base. By adding a compile step, we can validate that we have written sound JavaScript that is going to behave as we intended it to.

TypeScript generates JavaScript—it's as simple as that. This means that wherever JavaScript can be used, TypeScript can be used to generate the same JavaScript, but with added compile-time validations to ensure that it does not break certain rules. Having these extra validations before we even run the JavaScript is an immense time-saver, particularly where development teams are large, or where the resulting JavaScript is published as a library.

TypeScript also includes a Language Service, which can be used by tools such as code editors to help us understand how we should use JavaScript functions and libraries. These editors can then automatically provide a programmer with code suggestions and hints on how to use these libraries.

The TypeScript language, it's compiler, and associated tools helps JavaScript developers to be more productive, find bugs quicker, and help each other understand how their code should be used. It allows us to use tried and tested object-oriented concepts and Design patterns in our JavaScript code in a very simple and easy to understand manner. Let's try to understand how it does this.