在 function 声明中获取 function 参数类型

Question

I'm building a custom React hook which accepts an object (which has a function as one of the properties) as argument.

I want to get type definition on that function's arguments, which I am currently able to do like this:

  const { submitHandler, register } = useForm({
    handleSubmit: data => {
      /*
      Everything is ok:
      (parameter) data: {
          inputs: InputRefs;
          e: React.FormEvent<HTMLFormElement>;
      }
      */
    }
  });

However, I'd like to split the code by getting handleSubmit outside the useForm argument object like so:

  const handleSubmit = data => {
    // Parameter 'data' implicitly has an 'any' type, but a better type may be inferred from usage.
  };

  const { submitHandler, register } = useForm({ handleSubmit });

But if I do this, data is of type "any"... Is there a way to get the type definition for that function's arguments? Or the only and correct solution is really just export/import the type?

Sorry if this is not explicit or has already been explained, but I just started learning typescript and I can't seem to find what are the correct keywords to find the answer to what I am asking...

Thank you

Answer 1

Right-click on handleSubmit here:

const { submitHandler, register } = useForm({
    handleSubmit: data => {
      /*
      Everything is ok:
      (parameter) data: {
          inputs: InputRefs;
          e: React.FormEvent<HTMLFormElement>;
      }
      */
    }
  });

and choose "Go to Definition". That will give you the type you need to specify here:

const handleSubmit: ${Type} = data => {
    // Parameter 'data' implicitly has an 'any' type, but a better type may be inferred from usage.
  };

  const { submitHandler, register } = useForm({ handleSubmit });