Question

Is there any way to use some kind of DEBUG directive in JS code causing debug code not to be included in production? Examples:

// #if debug
console.log('Initializing');
// #endif

var url =
// #if debug
    '/foo/debug';
// #else
    '/foo';
// #endif

Answer 1

No. But you can simply replace console.log with a dummy function for production:

window.console = window.console || {};
window.console.log = function() { /* do nothing */ };

Then you just need to configure your build tools (assuming you have some) to include that code only in production builds.