Proper way to thoroughly write a JSON object typing - json

Question

In here: https://hackernoon.com/import-json-into-typescript-8d465beded79, I read it is possible to import JSON objects to my TypeScript project. I did that with the following JSON:
{
"defaultLanguage": "en",
"languageMap": {
"en": "English",
"pl": "Polish",
"de": "German"
}
}
I now want to make sure that any future changes to this file do not break my application so I introduced a following interface to the imported object:
export default interface IConfig {
defaultLanguage: string;
languageMap: ILanguage
}
interface ILanguage {
[language: string]: string
}
I have changed the typings.d.ts file:
declare module "*.json" {
const value: any;
export default value;
}
And imported to my Angular component:
import IConfig from './IConfig'; // Tried to put IConfig
// as a type in multiple places.
import * as config from './config.json';
(...)
private languageMap = config.languageMap; // in this line my Visual Studio Code
// underlines languageMap and shows
// the following error:
[ts] Property 'languageMap' does not exist on type 'typeof "*.json"'.
And below:
any
I am wondering if there is a way not to use (<any>config).languageMap but to include my IConfig interface, as suggested in the link above.

Answer 1

The module *.json module defines a wilds card module that will match any file ending with json and will type the json value as any. You can define a more specific module for config.json.
You can place a config.json.d.ts along side the config.json file describing the json:
//config.json.d.ts
interface IConfig {
defaultLanguage: string;
languageMap: ILanguage
}
interface ILanguage {
[language: string]: string
}
declare const value: IConfig;
export = value;
// usage.ts
import * as config from './config.json';
var languageMap = config.defaultLanguage; // All ok
Or if you use a module system taht does not support export=value you can use this definitions:
//config.json.d.ts
export let defaultLanguage: string;
export let languageMap: ILanguage
interface ILanguage {
[language: string]: string
}