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

//* currency
    $('#inv_currency').on('change', function () {
   
        var currency = $('.currency');
        if (this.value.trim() == '£') {
            currency.each(function (index) {
                var elem = $(this).contents().filter(function() {
                    return this.nodeType === 3;
                });
                var text = elem.text();
                elem[0].nodeValue = text.replace("€", "£");
            });
        } else {
            currency.each(function (index) {
                var elem = $(this).contents().filter(function() {
                    return this.nodeType === 3;
                });
                var text = elem.text();
                elem[0].nodeValue = text.replace("£", "€");
            });
        }
    });