DBScriptCache (db_script_cache.js) automatically caches script files in the browser's HTML5 client-side database. Rather than including your scripts using script tags, you include them using this script. The first time a user views the page the scripts will be pulled into the db and stored. On subsequent visits the scripts will be loaded from the db cache and not from your server. The script will continue to come from the cache until you supply a new version number or change the name of the script.
More info: DBScriptCache