JSFiddle - React, Tailwind, and code Playground

HTML

<body>
    <form>
        <div>
            <label>15. Schaalniveau</label>
            <div>
                <label>
                    <input type="radio" value="L" />Lokaal
                </label>
                <label>
                    <input type="radio" value="R" />Bovenlokaal/regionaal
                </label>
                <label>
                    <input type="radio" value="A" />Anders
                </label>
            </div>
        </div>
    </form>
</body>

JavaScript

var labels = document.getElementsByTagName('label');

for (var i = 0; i < labels.length; i++) {
    alert('t1');
    var br = document.createElement('br');
    labels[i].parentNode.insertBefore(br, labels[i].nextSibling);
}