如何将 class 类型作为参数传递？

Question

As described here: Declare class type with TypeScript (pass class as parameter) i can pass a class type as parameter.

There is a problem

export namespace customCommand {
    export class Command {
        public constructor(parameter?: any) {

        }
    }

    export function register(command: typeof Command) {
        new command()
    }
}

When i do this

customCommand.register(Map)

or

customCommand.register(Object)

There is no errors. I know that typeof Command and typeof Map both return the same result.

But how can i protect this and pass only Command type?

Answer 1

In TypeScript, you can construct a new type, something like:

type Class<T> = new (...args: any[]) => T

Which you can then use this way:

function register(command: Class<Command>) {
  new command()
}

This should constrain TypeScript to ONLY accept classes which construct or extend the Command type.

Answer 2

Maybe isPrototypeOf will do the trick for the classes extending the Command class:

export function register(command: any) {
    if (command === Command || Command.isPrototypeOf(command))
        new command()
}