I have a long script nicely wrapped into a (function() {/.../})() to avoid all kind of name pollution. It is 100% typed with zero warning.

I found out that Google Closure piler starts by redefining i and j in the global namespace which feels both unnecessary and dangerous, especially since I am piling a script that has zero interference with the namespace. (the piled script starts with var i=null,j=!1;, for pactness reasons I believe).

I can think of a work around which is to wrap it using the --output_wrapper but I can't think of a reason why Google would pollute the namespace like this.

Is there any?

I have a long script nicely wrapped into a (function() {/.../})() to avoid all kind of name pollution. It is 100% typed with zero warning.

I found out that Google Closure piler starts by redefining i and j in the global namespace which feels both unnecessary and dangerous, especially since I am piling a script that has zero interference with the namespace. (the piled script starts with var i=null,j=!1;, for pactness reasons I believe).

I can think of a work around which is to wrap it using the --output_wrapper but I can't think of a reason why Google would pollute the namespace like this.

Is there any?

• javascript
• google-closure-piler
• google-closure

• This is a similar example – abc123 Commented Aug 26, 2013 at 17:32
• possible duplicate of How to prevent Closure Compiler from renaming "true", "false" and "null" – Alexander Commented Aug 26, 2013 at 17:38
• Not quite, I already knew about the wrapper trick, which I mention in my post. I was looking for a reason to add a global scope while mine was empty. The answer seems to be, Closure piler does not car whether my scope was empty or not, it just makes the assumption that it can use it. – Mad Echet Commented Aug 26, 2013 at 17:48
• I edited the title to be more specific about what I was looking for. – Mad Echet Commented Aug 26, 2013 at 17:50
• btw, there is an option to disable this global vars - closure-piler.googlecode./svn/trunk/javadoc//google/… – dragn Commented Apr 22, 2014 at 16:47

1 Answer 1

The piler expects that it's given all relevant JavaScript so that it doesn't need to worry about clashes with other scripts. Therefore it assumes that it can unwrap the "unnecessary" anonymous function.

From the FAQ:

When using Advanced Optimizations, Closure Compiler adds new variables to the global scope. How do I make sure my variables don't collide with other scripts on the page?

Closure Compiler's advanced optimizations mode assumes that it's ok to add new variables to the global scope.

In JavaScript, it's often standard practice to wrap your code in an anonymous function, so that variables don't pollute the global scope. Closure Compiler has an --output_wrapper flag for exactly this purpose. Invoking it as --output_wrapper "(function() {%output%})();" will wrap your code in an anonymous function at pile-time.

Closure Compiler users often find it easier and simpler to do this wrapping at pile-time, rather than writing the anonymous function wrapper in the original source code.