How to type a constant with string-defined functions?

Solution 1:

Let's start typing EventHandler and figure this out.

First of all it's an object:

type EventHandlerType = {};

It has keys that are EVENTs

// Create a mapped type mapping events to anything
type EventHandlerType = { [e in EVENT]: any }

Every value is a function that takes a data parameter and returns void

// Create a mapped type mapping events to anything
type EventHandlerType = { [e in EVENT]: (data: any) => void };

Which should work in your code:

const EventHandler: { [key in EVENT]: (data: any) => void } = {
    [EVENT.FIRST_EVENT]: (data: any) => {
        console.log(`Hello there, ${data.blue_player}`);
    }
}

This is made simpler with the built in utility type Record which exists for these cases:

const EventHandler: Record<EVENT, (data: any) => void> = {
    [EVENT.FIRST_EVENT]: (data: any) => {
        console.log(`Hello there, ${data.blue_player}`);
    }
}

See mapped types in the docs for more examples and a drill down.