JSFiddle - React, Tailwind, and code Playground

by Elvis de Freitas

HTML

<textarea id="input"></textarea><br/>
<input type="checkbox" id="checkUpperCase" />
<input type="button" id="button2" value="convert" />

CSS

textarea {
  width: 100%;
  height: 150px;
}

JavaScript

$('#button2').click(function() {
  var text = $('#input').val();  
  var result = text.replace(/([A-Z])/g, "_$1");  
  var finalResult = $("#checkUpperCase").prop("checked")  ? result.toUpperCase() : result.toLowerCase();  
  $('#input').val(finalResult);
});