Loop forEach

var donuts = ["jelly donut" , "chocolate donut" , "glazed donut"];

donuts.forEach(function(donut){
donut += " hole";
dontu = donut.toUpperCaso();
console.log (donut);
});

var donuts = ["jelly donut", "chocolate donut", "glazed donut"];

// a variável `i` é usada para percorrer cada elemento na array
for (var i = 0; i < donuts.length; i++) {
    donuts[i] += " hole";
    donuts[i] = donuts[i].toUpperCase();
}