function calculator() {
    const html = { s1: "", s2: "", output: "" }

    function calc(a, b, sign) {
        const signs = { "+": (a, b) => a + b, "-": (a, b) => a - b }

        return signs[sign](Number(a), Number(b))
    }

    return {
        init: (a, b, c) => {
            html.s1 = document.querySelector(a)
            html.s2 = document.querySelector(b)
            html.output = document.querySelector(c)
        },
        add: () =>
            (html.output.value = calc(html.s1.value, html.s2.value, "+")),
        subtract: () =>
            (html.output.value = calc(html.s1.value, html.s2.value, "-")),
    }
}