Types for JavaScript.
WHAT IT IS
JavaScript with a static type system, compiled to plain JavaScript.
WHAT THAT MEANS
Nothing executes it directly. It is checked, then the types are removed.
WHAT IT PROVIDES
Errors caught before running Documentation of what functions expect Substantially better tooling Confidence when refactoring
WHAT IT DOES NOT PROVIDE
Any runtime guarantee.
WHY
Types are erased. Data arriving at runtime is unchecked.
WHAT THAT MEANS
External data must be validated regardless of its declared type.
WHAT ITS TYPE SYSTEM IS NOTABLE FOR
Expressiveness: unions, generics, conditional and mapped types.
WHAT THAT ENABLES
Describing shapes that dynamic code actually produces.
WHAT IT COSTS
A build step Some verbosity A learning curve for advanced features
WHEN IT IS WORTH ADOPTING
Any project with more than one developer, or maintained over time.
WHAT TO CONFIGURE
Strict checking, without which many benefits are absent.
WHAT TO AVOID
The type meaning anything, which disables checking entirely.
