Uso correcto e incorrecto funciones

 function calcular() {
                var x = document.getElementById("num1").value;
                var y = document.getElementById("num2").value;

                var gx = x;
                var gy = y;
                var w;
                while (y != 0) {
                    w = x % y;
                    x = y;
                    y = w;
                }

                var mcm = gx * gy / x;
                document.getElementById("resultado").value = mcm;
            }
            function calcularBien() {
                var x = document.getElementById("num1").value;
                var y = document.getElementById("num2").value;
                document.getElementById("resultado").value = minimoComunMultiplo(x, y);
            }

            function minimoComunMultiplo(x, y) {
                var gx = x;
                var gy = y;
                var w;
                while (y != 0) {
                    w = x % y;
                    x = y;
                    y = w;
                }
                return gx * gy / x;
            }
            var frase="Juanito";
            console.log(alReves('Viva la Pepa'));
            function alReves(frase){
                return frase.split('').reverse().join('');
            }