range.js

const range = (m, n) => Array(n).fill().map((_, i) => i+1).slice(m-1);

const expect = (input) => ({
    toEqual(expected) {
        const { stringify } = JSON;

        if (stringify(expected) !== stringify(input)) {
            throw Error(`expect ${expected} while ${input}`);
        } else {
            console.info('Pass');
        }
    }
});

expect(range(1, 2)).toEqual([1, 2]);