CODEWITHSUNDEEP
reactjstypescriptreact-native
Jo_cn
Jo_cn

Reputation: 105

What does the colon mean in Javascript after function?

I saw the Facebook F8 app code there is a ":" after the function

function setup(): React.Component {
  ...
}

What does this mean?

Inheritance?

Upvotes: 7

Views: 1738

Answers (2)

avalla
avalla

Reputation: 570

I think that is the return type of the function setup(), if you analyze different examples you will see that syntax in method parameters too

function user(state: State = initialState, action: Action): State {
  // some code
  return state;
}

edit: is flow, a static type checker from facebook: https://flow.org/

Upvotes: 3

Samuli Hakoniemi
Samuli Hakoniemi

Reputation: 19049

Usually it's flowtype annotation and in this case means that setup() returns a React.Component. Or it could be TypeScript as well, can't make sophisticated guess in this particular case.

Upvotes: 4

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