How to move core js files into the footer

You should not disturb core files, lets say even if you copy those files in footer and tomorrow wordpress releases another new version, and you update it. The files that you moved from /wp-includes/js/… will be back. In my opnion, try to minimize them. Although you be fine with wordpress core files, when optimizing your site and focus on optimizing html and css (and JS, if you made any)