JSFiddle - React, Tailwind, and code Playground

by Cam Gould

HTML

<input name="firstname" type="text" class="text" id="firstname" value="" onchange="populateDisplayName()"/>
 <input name="lastname" type="text" class="text" id="lastname" value="" onchange="populateDisplayName()"/>
 <input name="displayname" type="text" class="text" id="displayname" value=""/>
<script>
function populateDisplayName(){
    var firstName = document.getElementById('firstname');
    var lastName = document.getElementById('lastname');
    document.getElementById('displayname').value = firstName.value + ' ' + lastName.value;
}
</script>