логический

js/script.js

var val0 = true;
var even = false;
var val1;
function funMake() {
if(val0) {
document.write('Hello World!<br />');
}
else {
document.write('Привет Мир!<br />');
}
for(var i=0; i<=30; i++) {
if(even) {
if(i%2 == 0) {
document.write(i + '  ');
}
}
else {
if(i%2 != 0) {
document.write(i + '  ');
}
}
}
document.write('<br />');
document.write(Boolean(val1) + '<br />');
document.write(Boolean(null) + '<br />');
document.write(Boolean(0) + '<br />');
document.write(Boolean(-0) + '<br />');
document.write(Boolean(parseInt('Hello World!')) + '<br />');
document.write(Boolean('') + '<br />');
}

var val0 = true;
var even = false;
var val1;

function funMake() {
 if(val0) {
  document.write('Hello World!
');
 }
 else {
  document.write('Привет Мир!
');
 }
 for(var i=0; i<=30; i++) {
  if(even) {
   if(i%2 == 0) {
    document.write(i + '  ');
   }
  }
  else {
   if(i%2 != 0) {
    document.write(i + '  ');
   }
  }
 }
 document.write('
');
 document.write(Boolean(val1) + '
');
 document.write(Boolean(null) + '
');
 document.write(Boolean(0) + '
');
 document.write(Boolean(-0) + '
');
 document.write(Boolean(parseInt('Hello World!')) + '
');
 document.write(Boolean('') + '
');
}

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>