JSFiddle - React, Tailwind, and code Playground

HTML

<form method="POST" name="wordcount">
    <table border="0" cellspacing="0" cellpadding="0">
<tr>
<td width="100%"><textarea rows="12" name="wordcount2" cols="60"></textarea></td>
</tr>
<tr>
<td width="100%"><div align="right"><p><strong>
        <input type="button" value="Calcular precio" onClick="countit()"> €
    </input>
            <input type="text" name="wordcount3" size="20"> IVA incluido </input>
    </strong></p>
        </div>
    <div id="numP"></div>
 </td>
</tr>
</table>
</form>

JavaScript

function countit(){
    var formcontent=document.wordcount.wordcount2.value;
    formcontent = formcontent.trim();
    formcontent=formcontent.split(" ");
    numPalabras = formcontent.length;
    if(numPalabras >= 40000){
        document.wordcount.wordcount3.value = numPalabras*0.009;
    }else if(numPalabras >= 80000){
        document.wordcount.wordcount3.value = numPalabras*0.0085;
    }else{
        document.wordcount.wordcount3.value = numPalabras*(1/100);
    }
    document.getElementById("numP").innerHTML = numPalabras+" Palabras";
}