Function to determine the TypeScript type of a given value using a predefined list of types

typechecker.test.ts

import savedArtists from '../json-data/test/artists.json' assert { type: 'json'};
import { getType } from './typechecker';

// NOTE: These tests are a work in progress, 
as I have so far only completed work with the "Artist" type on the project at the time of writing
describe('Typechecker', () => {

	it('Correctly identifies and Artist', () => {
		const item = savedArtists[0];
		const type = getType(item);

		expect(type).toEqual(['Artist']);
	});

	it('Correctly identifies that an Artist is not an Album', () => {
		const item = savedArtists[0];
		const type = getType(item);

		expect(type).toEqual(
			expect.not.arrayContaining(['Album'])
		);
	});
});

typechecker.ts

import { resolve } from 'path';
import * as TJS from 'typescript-json-schema';

/**
 * Determine the TypeScript type of a given value
 * using a predefined list of types
 * @param item - The value to check
 * @returns string[] - Array of types specified in the function that the item satisfies
 */
export function getType(item: unknown): string[] {
	// If the given item is not an object, bail early and return its basic type
	if(typeof item !== 'object') {
		return [typeof item];
	}

	const typesToCheck = ['Artist', 'Album', 'Track'];
	const itemProperties = Object.keys(item);
	const matches = []; // Return an array in case the given item satisfies more than one of the given types

	const program = TJS.getProgramFromFiles(
		[resolve('./api/types.ts')] // File containing the type definitions for the typesToCheck listed above
	);

	// Generate JSON schema object for each given type
	// required: true is, well, required, so we can check the given item's keys against the required properties of the type i.e. the ones we 100% expect to be present
	[...typesToCheck].forEach((type) => {
		const schema = TJS.generateSchema(program, type, { required: true });  

		if(schema.required.every(v => itemProperties.includes(v))) {
			matches.push(type);
		}
	});

	if(matches.length > 1) {
		console.warn('Type check returned more than one match. This may lead to unexpected results.');
	}

	return matches;
}