What is the best way to create a type that excludes the character 'a' from a string?

Here is how I am attempting to define a specific type:

type Response = {
   type: 'a',
   value: string
} | {
   type: ???, // any other string except 'a'
   value: number
}

Do you think this can be done?

I experimented with the following code:

type OtherStrings = Exclude<string, 'a'>

However, it did not yield the results I was hoping for.

Answer №1

It seems like there may not be a better solution than this

type DifferentWords<S> = S extends 'x' ? never : string

const DifferentWords: DifferentWords<'y'> = 'y'
const DifferentWords: DifferentWords<'x'> = 'x' // error

PS. Instead of using workarounds like the one above, it's recommended to explicitly list all possible strings that should be allowed or disallowed.

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