JSFiddle - React, Tailwind, and code Playground

HTML

<form name="forma" method="POST" action="used-results.php" id="apliforma">

    <select>
  <option value="">Select one</option>
  <option value="saab">Saab</option>
  <option value="mercedes">Mercedes</option>
  <option value="audi">Audi</option>
</select>
    <button type="submit" id='submit' >submit</button>
</form>

JavaScript

$(document).ready(function (){
    validate();
    $('select').change(validate);
});

function validate(e){
    
    var validation = true;
    $('input , select').each(function(){ 

        if($(this).val().length>0)
        {
            validation = false;
        }
    });   
   
    if ( validation ) {
        $('#submit').prop('disabled', true);
  
    } else {
   
        $('#submit').prop('disabled', false);
    }
}