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Kaan G
Kaan G

Reputation: 219

How to define a type for string | number?

I have a map function and my function's parameter's type is an array of strings or number. I'm defining it like:

(param: (string | number)[]) => ...

however I want to beauty it like: 

(param: StringOrNumber)[]) => ...

since I'm using that param in many functions and found that pipeline in middle decreases readibility. Is there a way to do that by default in Typescript or am I need to define a custom type for that?

Upvotes: 2

Views: 1947

Answers (2)

Brian Mullin
Brian Mullin

Reputation: 46

You would need to define a custom type for this, like type StringOrNumber = string | number. However, if you include a custom type such as this in a declaration file (eg. in a file named types.d.ts, where the .d.ts suffix indicates to the TypeScript compiler that it is a declaration file) somewhere in your project, then that type will be globally available in the other files in your project.

I would recommend reading up on declaration files in the documentation here, though it's not super clear. https://www.typescriptlang.org/v2/docs/handbook/declaration-files/introduction.html

Upvotes: 2

satanTime
satanTime

Reputation: 13539

you need to define a new type and use it everywhere, that's totally fine, or you could use Array<string | number>, what is more readable IMO.

Upvotes: 0

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