аргументы функции

js/script.js

function funMake(agr0, arg1, arg2) {
var res = agr0 + arg1 + arg2;
document.write(res + '<br />');
}

function funMake(agr0, arg1, arg2) {
 var res = agr0 + arg1 + arg2;
 document.write(res + '
');
}

index.html

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>New Page</title>
<script src="js/script.js"></script>
</head>
<body>
<script>
funMake(10, 20, 30);
funMake(10, 20, null);
funMake(10, null, null);
</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(10, 20, 30);
funMake(10, 20, null);
funMake(10, null, null);
</script>
</body>
</html>