Obtain 5 last values of an array in javascript?

You can do it using the splice function, passing as a parameter the position from where you want to cut.

let aNumeros=[1, 5, 6, 7, 8, 9, 10, 12];
let aNuevo = aNumeros.slice(aNumeros.length-5)
console.log(aNuevo)

In this case, as the starting position, we pass the length of the array (aNumeros) and subtract 5, so we will always look for the last 5.

Note: If there is no end position, it will leave a new array with the elements from the start position and until the end.

Take a look at the documentation, to see how it works in more detail   link

In order to respond to your concern I share the following code segment, I hope you find it useful, greetings:

<script>
  // uso del evento ready de jQuery para generar el example requerido
  $(function() {

    // arreglo inicial (en orden aleatorio)
    var aNumeros=[1, 6, 5, 8, 7, 9, 12, 10];

    // impresion de arreglo inicial
    console.log("aNumeros: " + aNumeros.toString());

    // arreglo ordenado usando function nativas de js
    var arrOrdenado = aNumeros.sort(function(a, b){return a - b});

    // impresion de arr ordenado
    console.log("arrOrdenado: " + arrOrdenado.toString());                
    // uso de la function slice luego del ordenamiento para cortar 

    var aNuevo = arrOrdenado.slice(arrOrdenado.length-5)                
    // impresion del arr que requieres...
    console.log("aNuevo: " + aNuevo.toString());                
    // fin de function ready de jQuery          
  });
// fin de segmento de javascript
</script>