JSFiddle - React, Tailwind, and code Playground

HTML

<input onclick="txt()" type="number" min="0" max="3" size="4" value="0" id="iptnbr">



<textarea id="txt1" class="txt">1</textarea>
<textarea id="txt2" class="txt">2</textarea>
<textarea id="txt3" class="txt">3</textarea>

CSS

.show {
  display: block;
}

.txt {
  display: none;
}

JavaScript

function txt() {
var qteValue = document.querySelector('#iptnbr').value;
// reset sauvage
      document.getElementById("txt1").className="show txt"
      document.getElementById("txt2").className="show txt"
      document.getElementById("txt3").className="show txt"

      if(qteValue == 1)
      {
      document.getElementById("txt1").classList.toggle('txt');
      }
      else if (qteValue == 2)
      {
      document.getElementById("txt1").classList.toggle('txt');
      document.getElementById("txt2").classList.toggle('txt');
      }
       else if (qteValue == 3) 
      {
      document.getElementById("txt1").classList.toggle('txt');
      document.getElementById("txt2").classList.toggle('txt');
      document.getElementById("txt3").classList.toggle('txt');
      }
}