如何在TypeScript中的rest参数之后指定回调函数？

Question

I have a function that receives an some arbitrary number of strings like in this example:

function foo(...strings, callback);

How do I specify it's types in typescript? I weighed the following alternatives:

1. functio foo(...strings: string, callback: (err: Error, res: any) => void);

this is no good because rest parameters have to be last.

2. foo(...strings: any);

this is a compromise that will compile but requires forfeiting type checking.

3. foo(...strings: string|((err: Error, res: any) => void));

this is a bit more true but is very non-readable and I don't think I saw it in any project.

Is there a best practice to deal with this? What trade offs should be taken into account?

Answer 1

This is not possible, you have to change your 'order style', and put your callback before your rest parameters. That would be a better (more readable and more type safe) solution than the other awkward workarounds you listed.