JSFiddle - React, Tailwind, and code Playground

HTML

<div>
Your name:
<input type="text"  placeholder="World">
<hr>
Hello <span id="changeVal">World</span> !
</div>

JavaScript

var input = $('input'),
    span = $('#changeVal');
input.on('keyup',function(){
  span.text(input.val() ? input.val() : 'World');
});