My Solution!

var correctAnswer = 0;
var rankCrown;
//Quiz1
var quiz1 = prompt("What equals 1 + 2?");
if (parseInt(quiz1) === 3) {
  alert("Correct! Move onto Quiz 2.");
  correctAnswer += 1;
}
else {
  alert("Sorry, you're wrong. Move onto Quiz 2.");
}
//Quiz2
var quiz2 = prompt("What is the captial of Netherlands?");
if (quiz2.toUpperCase() === "AMSTERDAM") {
  alert("Correct! Move onto Quiz 3.");
  correctAnswer += 1;
}
else {
  alert("Sorry, you're wrong. Move onto Quiz 3.");
}
//Quiz3
var quiz3 = prompt("Who invented the ligt bulb? Type the last name only.");
if (quiz3.toUpperCase() === "EDISON") {
  alert("Correct! Move onto Quiz 4.");
  correctAnswer += 1;
}
else {
  alert("Sorry, you're wrong. Move onto Quiz 4.");
}
//Quiz4
var quiz4 = prompt("When the world war 2 began?");
if (parseInt(quiz4) === 1938) {
  alert("Correct! Move onto Quiz 5.");
  correctAnswer += 1;
}
else {
  alert("Sorry, you're wrong. Move onto Quiz 5.");
}
//Quiz5
var quiz5 = prompt("What is the best programming language?");
if (quiz5.toUpperCase() === "JAVASCRIPT") {
  alert("Correct! You finished the quiz.");
  correctAnswer += 1;
}
else {
  alert("Sorry, you're wrong. You finished the quiz.");
}
//Assigning a crown level
if (correctAnswer === 5) {
  rankCrown = "Gold Crown";
}
else if (correctAnswer === 4 || correctAnswer === 3) {
  rankCrown = "Silver Crown";
}
else if (correctAnswer === 2 || correctAnswer === 1) {
  rankCrown = "Bronze Crown";
}
else {
  rankCrown = "No Crown";
}
//Printing a phrase
document.write("<p>Congraturation! You've answered " + correctAnswer + " questions correct. You achieved a " + rankCrown +" .</p>");