typescript generics 的默认参数

Question

Say I have

const myFunc = <T, > (data: T) => {
  return data?.map((d) => ({name: d.name})
}

Ts throws an error saying: Property 'name' does not exist on type 'T' , which makes sense so I can fix it with

const myFunc = <T extends {name: string}> (data: T) => {
  return data?.map((d) => ({name: d.name})
}

but the problem is that because I wanted T to be generic if I then call this function with

myFunc(x: number)

I get an error saying the types do not match, but I want it to match the type I pass in?

I should make something else clear I have a react component that has a prop called myFunc and the myFunc I've defined below is the default prop but a user could pass their own in

Answer 1

Well by extending the type like that, the type needs to be an object that contains a name.

So try this

const myFunc = <Type extends {name: string} | number> (data: Type) => {
  return data?.map((d) => ({name: d.name})
}

(T i deprecated, so using Type instead)