05. Sum - v2 - using the "Revealing Module" pattern

  function getModel() {
    let num1;
    let num2;
    let result;

    function init(selector1, selector2, resultSelector) {
      num1 = document.querySelector(`${selector1}`);
      num2 = document.querySelector(`${selector2}`);
      result = document.querySelector(`${resultSelector}`);
    }

    function add() {
      action((a, b) => a + b);
    }

    function subtract() {
      action((a, b) => a - b);
    }

    function action(operation) {
      const val1 = Number(num1.value);
      const val2 = Number(num2.value);
      result.value = operation(val1, val2);
    }

    const model = { init, add, subtract };
    return model;
  }