TypeScript 2.x By Example

Types in TypeScript

The JavaScript language does not have a concept of explicitly defining types of variables which end up being one of the main reasons for errors at runtime. We can assign one type to a variable and then later assign a different type to the same variable. TypeScript, with its type annotation, allows us to assign types to each variable, function, object, or class. Types act as a contract, which that variable has to follow, and the TypeScript compiler makes sure that there are no deviations from this contract. TypeScript does this with static and dynamic type checking. Types provide a set of rules which the compiler needs to follow for that variable; these rules also allow an autosuggest feature in IDEs by providing the most ...