JSFiddle - React, Tailwind, and code Playground

HTML

<h1> Escolha as 2 opções</h1>
<input type="checkbox"onclick="teste()"id="primeiro"></input>
    <br>
        <input type="checkbox"onclick="teste1()"id="segundo">
        </br>
        
    <input type="text"id="teXt">
        <script>
            var line="";
           function teste()
    {
        if (document.getElementById('primeiro').checked==true)  {
            line="font-style:italic;"
        }
        else
        {
            line=""
        }
       document.getElementById("teXt").value=line+line1;   
    };
            
            
               var line1="";
           function teste1()
    {
        if (document.getElementById('segundo').checked==true)  {
            line1="font-weight:bold;"
        }
        else
        {
            line1=""
        }
       document.getElementById("teXt").value=line1+line;   
    }
        </script>