конструктор

js/script.js

function Obj(arg0, arg1) {
this.val = arg0;
this.str = arg1;
this.fun = function() {
for(var i=0; i<this.val; i++) {
document.write(this.str + '<br />');
}
}
}
function funMake() {
var O = new Obj(5, 'Hello World!');
O.fun();
}

function Obj(arg0, arg1) {
this.val = arg0;
this.str = arg1;
this.fun = function() {
for(var i=0; i<this.val; i++) {
document.write(this.str + '<br />');
}
}
}
function funMake() {
var O = new Obj(5, 'Hello World!');
O.fun();
}

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>