How to use "as const" on dynamically generated objects in TypeScript?

As the title suggests I've been trying every possible way and solution that I could find online to use "as const" on a dynamic object but no luck whatsoever so I would greatly appreciate any help.

What I'm trying to achieve is generating an object THEME_NAME_LIST of the keys used in another object THEME, so that I don't have to manually maintain the THEME_NAME_LIST object every time some supposedly new key gets to the THEME object.

I've been easily able to generate const types from my object up until this point only on statically typed objects like this;

export const THEME_NAME_LIST = {
	DARK: 'dark',
	LIGHT: 'light',
} as const;


const THEME_ARRAY = Object.values(THEME_NAME_LIST);
export type ThemeType = typeof THEME_ARRAY[number];

And when I hover over theTHEME_NAME_LIST.LIGHT, the IDE shows the following message;

> (property) LIGHT: "light"

Now everything up until this point works great!
However, when I change THEME_NAME_LIST to the example below, the THEME_NAME_LIST breaks!

const THEME = {
	// ...
	DARK: {
		// ...
	},
	LIGHT: {
		// ...
	},
	// ...
};

export const THEME_NAME_LIST = {} as const;
Object.keys(THEME).forEach((key) => {
	const THEME_NAME = key.toUpperCase();
	THEME_NAME_LIST[THEME_NAME] = key.toLowerCase();
});

So when I hover THEME_NAME_LIST.LIGHT, the IDE prompts the following message;

> Property LIGHT does not exist on type {}

Is anybody able to tell me what I'm doing wrong?

const assertions are not meant for dynamic objects. It tells the compiler your object is readonly. Your above code gives an error when you try to manipulate the object.

Element implicitly has an 'any' type because expression of type 'string' can't be used to index type '{}'.
  No index signature with a parameter of type 'string' was found on type '{}'.(7053)

Instead of applying const to the object you're trying to create, apply the const assertion on your original object, and derive types from there. I would suggest creating a mapped type like so:

type ThemeNameList = {
  [ThemeName in keyof typeof THEME as Uppercase<ThemeName>]: Lowercase<ThemeName>;
};

Note that functions like Object.keys won't help preserve string literals. You can place assertions at any point in time, but my suggestion would be to only apply the ThemeNameList as an assertion to your new object right before you export.

const _THEME_NAME_LIST: Record<string, unknown> = {};
Object.keys(THEME).forEach((key) => {
  const THEME_NAME = key.toUpperCase();
  _THEME_NAME_LIST[THEME_NAME] = key.toLowerCase();
});

export const THEME_NAME_LIST = _THEME_NAME_LIST as ThemeNameList;