Types are painfully helpful

The types are working even if they irritate you. And even more of that. The more typechecking is a pain the bigger the benefits.

Retrieving keys for the React components

React has its quirks. The 'key' property React asks to set for the components, rendered within an iteration of any kind, are amongst them.

Distinguish types at runtime

Often, using the typescript, you have to handle situations when you don't know the type beforehand, during the compilation time.