I just found this plugin. Haven’t tried it yet but it looks good and will hopefully save me much time. It seems from lines 33–47 of the wp-js-compress.php file in the version 2.0.6 code, that the gzip’d version is indeed cached.
if(extension_loaded('zlib') && substr_count($_SERVER['HTTP_ACCEPT_ENCODING'], 'gzip')){
ob_start('ob_gzhandler');
header('Content-Encoding: gzip');
} else {
ob_start();
}
header("Content-type: text/javascript; charset: UTF-8");
header("Cache-Control: max-age=".$wp_js['cache']);
header("Expires: " .gmdate("D, d M Y H:i:s", time() + $wp_js['cache']) . " GMT");
if (!wp_js_is_expired($wp_js['file']) && @file_exists('cache/'.wp_js_filename($wp_js['file']))) {
include('cache/'.wp_js_filename($wp_js['file']));
} else {
ob_start("wp_js_clean");
peace~