Why `export const INCREMENT_ENTHUSIASM` then `export type INCREMENT_ENTHUSIASM` again
yeongjet opened this issue · 2 comments
Why export const INCREMENT_ENTHUSIASM then export type INCREMENT_ENTHUSIASM again, what's the meaning?
You can open src/actions/index.tsx to understand more.
Hi @yeongjet, have a look at typeof type guards and string literal types.
Basically, it means a variable that has the type INCREMENT_ENTHUSIASM can only has 'INCREMENT_ENTHUSIASM' as a value (in other words, it can't only be a string, it must also has this specific text as a value).
It's the same as writing export type INCREMENT_ENTHUSIASM = 'INCREMENT_ENTHUSIASM'.
On line 2 value INCREMENT_ENTHUSIASM is exported.
On line 3 type INCREMENT_ENTHUSIASM is exported.
TypeScript is smart enough to know when a variable is used as a value, and when it is used as a type.