JSFiddle - React, Tailwind, and code Playground

HTML

<select id="inv_currency">
    <option value="£">£</option>
    <option value="€">€</option>
</select>
<span class="invE_balance currency">
£
<span>0.00</span>
</span>

JavaScript

$('#inv_currency').on('change', function () {
        $('.currency').each(function (index, elm) {
            var elem = $(elm).contents().filter(function () {
                return this.nodeType === 3;
            }).get(0);
            elem.nodeValue = elem.nodeValue.replace(/(\€|\£)/g, function(x) {
                return x == '€' ? '£' : '€';
            });
        });
    });