Preventing closure compiler from renaming certain variables

Question

I have a javascript file with a global object that must not be renamed (_gat from the Google Analytics async tracker).

This object must not be renamed by the Google Closure Compiler as Google Analytics looks for a variable with this specific name.

I've looked into the Javascript Doc notations that are mentioned: http://code.google.com/closure/compiler/docs/js-for-compiler.html - However, I cannot find anything regarding the "protection" of a variable.

The problem exists no matter if I use simple or advanced compilation.

How can I ensure that the _gat variable is not renamed?

Answer 1

Use the goog.exportSymbol function from base.js. Documentation is here: http://closure-library.googlecode.com/svn/docs/closure_goog_base.js.html

Usage is like

goog.exportSymbol("_gat", _gat)

Answer 2

If it isn't declared as part of the code you are compiling than an extern declaration is appropriate: http://code.google.com/closure/compiler/docs/api-tutorial3.html#externs

Answer 3

Using Closure Compiler web app, you can set js_externs. Refer to Advanced Compilation and Externs for more examples.

// ==ClosureCompiler==
// @compilation_level ADVANCED_OPTIMIZATIONS
// @output_file_name default.js
// @js_externs _gat
// ==/ClosureCompiler==