JSFiddle - React, Tailwind, and code Playground

HTML

<select id="logintype">
<option selected>...</option>
<option>1</option>
<option>2</option>
</select>
<form id="loginf">
    <input type="text" id="user" class="textbox">
    <input type="text" id="pass" class="textbox">
</form>

JavaScript

$('#logintype').change(function() {
      if ($(this).val() == 1) {
       $('#loginf').attr('action','login1.php');
       $('#loginf #user').attr('name', 'userid')[0].defaultValue = 'Username';
       $('#loginf #pass').attr('name', 'password')[0].defaultValue= 'password';
      }
      else {
       $('#loginf').attr('action','login2.php');
       $('#loginf #user').attr('name', 'email')[0].defaultValue = 'Email';
       $('#loginf #pass').attr('name', 'passed_password')[0].defaultValue = 'password';
      };
     });
    
     $('.textbox').focus(function(){
      if (this.value == this.defaultValue) {
       this.value = '';
      };
     });
    
     $('.textbox').blur(function(){
      if (this.value == '') {
       this.value = this.defaultValue;
      };
     });