How to automatically attribute links with nofollow, only for a SPECIFIC html element in a webpage?

Question

Some time ago I found this good old No Follow script, to add a nofollow attribute to hyperlinks. However, I dont want this script to be a site-wide thing! I just want hyperlinks inside a certain html element (say for example <article> ...</article>) to be attributed with a nofollow. How can one adapt the below script to achieve this?

<script type='text/javascript'>
    var a = $(this);
    var href = a.attr('href');
    $(document).ready(function(){
        $("a[href^='https://']").each(function (){
            if(this.href.indexOf(location.hostname) == -1) {
                $(this).attr('rel', 'nofollow');
            }
        });
    }); 
</script>

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Note: in essence, my question is the exact opposite of this question: "Nofollow for the whole page?"