Dependent types are an interesting feature in TypeScript: Not only do they show what is happening in a program. They also prepare the code for things to come.

TypeScript language The TypeScript language accepts JavaScript as valid, but offers the additional options of type annotations, type checking at compile time, classes, and modules.

Next TypeScript release, due February 25, will support a limited form of checking against conditional and indexed acces types in return statements.

Less than two weeks after publishing the TypeScript 2.8 Release Candidate, Microsoft has officially launched it into general availability, bringing conditional types and more.

If you tell TypeScript what your range of data types is ("constrain your data type"), then TypeScript will let you use any functionality that's common to those data types. You implement constraints on ...