JSFiddle - React, Tailwind, and code Playground

HTML

<span class="currency" name="499">499</span> <br />
<span class="currency" name="15">15</span> <br />
<input type="button" id="showInEuro" value="Click" /> <br />

JavaScript

var usdToEuroExchRate = 1.5;

    $("#showInEuro").click(function() { 
        $("span.currency").each(function(index) { 
            $(this).text($(this).attr("name") * usdToEuroExchRate);
        });
    });