JSFiddle - React, Tailwind, and code Playground

HTML

<select id="tipos" placeholder="Tipo de documento">
<option value="prim" disabled selected>Tipo de DNI</option>
<option value="sdni">DNI</option>
<option value="spass">Pasaporte</option>
</select>
 



<input type="number"  id="txt"  disabled/>
  

 

<br />

JavaScript

///////

document.getElementById('tipos').onchange = (function(){
     
 
    
    if(this.value=="sdni"){
   
    
       
     document.getElementById('txt').maxLength=8;
     document.getElementById('txt').disabled=false;
       
         
    }
    else if(this.value=="spass"){
     			 
          document.getElementById('txt').disabled=false;		document.getElementById('txt').maxLength=12;   
          
    }
     
    {
 
    document.getElementById('txt').value="";
   
      }
});