JSFiddle - React, Tailwind, and code Playground

HTML

<div id='_form'>
    Form Inputs
</div>

<div id='_preview' style='display: none'>
    Preview
</div>

<button id='_toggle'>
   Toggle
</button>

<script>
window._toggle.onclick = () => previewFormInputs();
// can also do the following instead of the above
/* window._toggle.onclick = previewFormInputs; */

function setElementVisibility(element, visible) {
    element.style.display = visible ? 'inherit' : 'none';
}

let _previewVisible = false;
function previewFormInputs() {
    _previewVisible = !_previewVisible;
    setElementVisibility(window._form, !_previewVisible);
    setElementVisibility(window._preview, _previewVisible);
}
</script>