if...else

js/script.js

var val = true;
function funMake() {
if(val) {
document.write('Hello World!' + '<br />');
}
else {
document.write('To be or not to be?' + '<br />');
}
}

var val = true;

function funMake() {
 if(val) {
  document.write('Hello World!' + '
');
 }
 else {
  document.write('To be or not to be?' + '
');
 }
}

index.html

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>New Page</title>
<script src="js/script.js"></script>
</head>
<body>
<script>
funMake();
</script>
</body>
</html>

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>New Page</title>
<script src="js/script.js"></script>
</head>
<body>
<script>
funMake();
</script>
</body>
</html>