What kind of JavaScript can the w3compiler not handle?
By default, the safety level of the w3compiler is tuned to avoid JavaScript that it cannot handle, so you should feel safe optimizing these types of files in general. While you should always test code optimization first, w3compiler should compress most JavaScript flawlessly. The most troubling code that we see used is dynamically evaluated — some forms of self-rewriting script cannot be determined with interpretation, which may depend on user conditions. For the bold, the advanced features of w3compiler allow you to tune the software to avoid making default, conservative assumptions in optimization. If you know what you are doing, you can probably squeeze another 5-10% file size reduction out of some scripts by adjusting w3compiler’s JavaScript safety settings.
