05. Sum - using the "Module" pattern

 function getModel() {
    const model = (() => ({
      init(selector1, selector2, resultSelector) {
        model.num1 = document.querySelector(`${selector1}`);
        model.num2 = document.querySelector(`${selector2}`);
        model.result = document.querySelector(`${resultSelector}`);
      },
      add: () => model.action((a, b) => a + b),
      subtract: () => model.action((a, b) => a - b),
      action(operation) {
        const val1 = Number(model.num1.value);
        const val2 = Number(model.num2.value);
        model.result.value = operation(val1, val2);
      },
    }))();

    return model;
  }