types-kit.literaltoprimitive.md

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LiteralToPrimitive type

Given a literal type return the Primitive it belongs to, or never if it's not a primitive. eg: Working with generic types that may be literal types.

Signature:

export type LiteralToPrimitive<T> = T extends number
  ? number
  : T extends bigint
  ? bigint
  : T extends string
  ? string
  : T extends boolean
  ? boolean
  : T extends symbol
  ? symbol
  : T extends null
  ? null
  : T extends undefined
  ? undefined
  : never

Example

function foo<T>(v: T): T {
 return v
}
function bar<T>(v: T): LiteralToPrimitive<T> {
 return v
}

foo(1) // 1
foo('foo') // 'foo'
bar(1) // number
bar('foo') // string