Where to register Java Script code?

Where to register Java Script code?
Dear friends
In any template files you need to put the java script code? Script to work on all pages site

<!-- Begin CallBox code -->
<script >
        (function() {
        var d = new Date();
        var em = document.createElement('script'); em.type = 'text/javascript'; em.async = true;
                em.src = ('https:' == document.location.protocol ? 'https://' : 'https://')
                + 'callbox.by/js/callbox.js?' + d.getTime(); var s = document.getElementsByTagName('script')[0];
                s.parentNode.insertBefore(em, s);
        })();
</script>
<!-- End CallBox code -->