Fns.js

const sucessor = (n) => {
  return n + 1;
};

const somarNaturais = (x, y, acc=y, coun=x) => {
  return x <= 0 && y || (!!coun) && somarNaturais(x, y, sucessor(acc), coun-1) || acc;
};

// Range melhorado
function reverse([x, ...xs]) {
  return x !== void 0 && [...reverse(xs), x] || []
}

intervaloAux = function (x, y) {
  return ( x <= y ) && [ x, ...intervaloAux( x+1, y ) ]
    || x === void 0 && [ x, ...intervaloAux( x-1, y ) ] 
    || [];
}	

var intervalo = function( x, y ) {
  return (y < x) && reverse(intervaloAux(y, x)) || intervaloAux(x, y)
};


const compararListas = ( xs, ys, aux=0) => {
  return aux <= xs.length 
     ? xs[aux] === ys[aux] && compararListas(xs, ys, aux+1) 
     : true;
};