function isPrimeFocus(where) {
var buttonEl = document.getElementById("is-prime-button");
buttonEl.innerHTML = "Is Prime?";
buttonEl.style.backgroundColor = "LightBlue";
}
function isPrimeClick(where) {
var inputEl = document.getElementById("number");
var numStr = inputEl.value;
var number = parseInt(numStr);
var answer;
var color;
if (isNaN(number)) {
answer = "¿%^@!?";
color = "Yellow";
} else if (isPrime(number)) {
answer = "\u2713"; // checkmark
color = "LawnGreen";
} else {
answer = "\u2A02"; // X symbol
color = "Red";
}
var buttonEl = document.getElementById("is-prime-button");
buttonEl.innerHTML = answer;
buttonEl.style.backgroundColor = color;
}
function isPrime(x) {
if (x <= 1) return false;
for (var i = 2; i < x; i++) {
if (x % i == 0) {
return false;
}
}
return true;
}