JSFiddle - React, Tailwind, and code Playground
HTML
<input type="radio" name="contact" value="0" checked/>E-Mail <br />
<input type="radio" name="contact" value="1"/>Telefax <br />
<input type="radio" name="contact" value="2"/>Brief <br />
<div id="forms">
<div id="form-email" class="form">
<ul>
<li>
<label>Vorname:</label>
<input type="text"/>
</li>
<li>
<label>Nachname:</label>
<input type="text"/>
</li>
<li>
<label>E-Mail Adresse:</label>
<input type="text"/>
</li>
</ul>
</div>
<div id="form-telefax" class="form">
<label>Irgendwas... xD:</label>
<input type="text"/>
</div>
<div id="form-brief" class="form">
<ul>
<li>
<label>Vorname:</label>
<input type="text"/>
</li>
<li>
<label>Nachname:</label>
<input type="text"/>
</li>
<li>
<label>Nachricht</label>
<textarea></textarea>
</li>
</ul>
</div>
</div>
CSS
.form{ display: none;}
JavaScript
$(function(){
var $forms = $('#forms'),
speed = 100;
$forms
.find('.form:first')
.show()
.addClass('show');
$('input[name=contact]').change(function (){
if($(this).is(':checked')){
$forms
.find('.show')
.hide(speed)
.removeClass('show')
.end()
.find('.form:eq('+$(this).val()+')')
.show(speed)
.addClass('show')
}
})
})