JSFiddle - React, Tailwind, and code Playground

HTML

<textarea class="mapCode">
   <area shape="rect" coords="" href="http://www.sitehere" target="_self">
</textarea>

JavaScript

var selection = {
    x1: 1,
    x2: 2,
    y1: 1,
    y2: 2
};

var $content = $('<div/>').html($('.mapCode').val());
$content.find('area').attr('coords', selection.x1+','+selection.y1+','+selection.x2+','+selection.y2);

$('.mapCode').val($content.html());