javascript，PHP - 如果输入字段不为空，则需要字段

Question

i want to make input id='pass2' required if input id='pass1 value.lenght != null.

<form action="perfil.php" method="post">
<table  width="100%" border="0">
<tr>
<td width="10" height="10"></td>
<td colspan=2><p align=justify></p></td>
<td width="4"></td>
</tr>
<tr>
<td width="10" height="10"></td>
    <td align="left"><font color=#ff0000 id="atencao" size="2em"></font></td>
     <td width="4"></td>
    </tr>
    <tr>
     <td></td>
  <td align="left">Password:</td>
  <td align="left"><input AUTOCOMPLETE=OFF type=password value="" id="password" name="password" style="WIDTH:140px;" maxlength="254" required></td>   
  </tr>
    <tr>
  <td></td>
  <td align="left">New Password :</td>
  <td align="left"><input AUTOCOMPLETE=OFF type=password value="" id="pass1" name="pass1" style="WIDTH:140px;" maxlength="254"></td>
   <td></td>
   </tr>
   <tr>
   <td></td>
   <td align="left">
    Confirm Password :</td>

 <td align="left"><input AUTOCOMPLETE=OFF type="password" value="" id="pass2" name="pass2" style="WIDTH:140px;" maxlength="254" onkeyup="checkPass(); return false;"></td>
  <span id="confirmarMessagem"></span>
<td></td>

I want to require pass2 if pass1value.lenght is not null on submit or when the field starts gettings input != null.

Answer 1

This help you :

<script>
  var pass1 = document.getElementById("pass1");
  var pass2 = document.getElementById("pass2");
  pass2.oninput = function(){
         if((pass2.value).length > 0)
             pass1.required = true;
            }  
</script>