How can you define a Decorator interface in TypeScript

Question

I am learning TypeScript and I would like to define an interface for function decorators : function that accept a function and return a function.

Here is a snippet that gives the flavor of what I am trying to define:

interface IDecoratorFn {
    (fn:function):function
}

Can this interface be specified in TypeScript ?

Answer 1

You're almost there, just need to use Function instead of function :

interface IDecoratorFn {
    (fn: Function): Function;
}

You can also define a type alias:

type IDecoratorFn = (fn: Function) => Function;

Answer 2

typescript has built-in types.

• PropertyDecorator
• ClassDecorator
• MethodDecorator
• ParameterDecorator

In your case, use MethodDecorator as type directly