[JS] Controllo sui Checkbox e Select

[Fobos87]

Salve a tutti,

Ho un problema, vorrei che al check ed al uncheck di un mio input checkbox si checkano e uncheckano gli altri

<script language="javascript">
 function copiastato() {
   if (document.getElementById('manufacturer').checked==true) {   
       document.getElementById('manufacturer1').checked=true;
       document.getElementById('manufacturer2').checked=true;
       document.getElementById('manufacturer3').checked=true;
       document.getElementById('manufacturer4').checked=true;
   } else {
       document.getElementById('manufacturer1').checked=false;
       document.getElementById('manufacturer2').checked=false;
       document.getElementById('manufacturer3').checked=false;
       document.getElementById('manufacturer4').checked=false;
   };
   if (document.getElementById('Vendor').checked==true) {   
       document.getElementById('Vendor1').checked=true;
       document.getElementById('Vendor2').checked=true;
       document.getElementById('Vendor3').checked=true;
       document.getElementById('Vendor4').checked=true;
   } else {
       document.getElementById('Vendor1').checked=false;
       document.getElementById('Vendor2').checked=false;
       document.getElementById('Vendor3').checked=false;
       document.getElementById('Vendor4').checked=false;
   };
}
</script>

<input type="checkbox" name="manufacturer" id="manufacturer" value="1" onClick="copiastato();">manufacturer
<input type="checkbox" name="manufacturer1" id="manufacturer1" value="1" disabled>manufacturer1
<input type="checkbox" name="manufacturer2" id="manufacturer2" value="1" disabled>manufacturer2
<input type="checkbox" name="manufacturer3" id="manufacturer3" value="1" disabled>manufacturer3
<input type="checkbox" name="manufacturer4" id="manufacturer4" value="1" disabled>manufacturer4

<input type="checkbox" name="Vendor" id="Vendor" value="1" onClick="copiastato();">Vendor
<input type="checkbox" name="Vendor1" id="Vendor1" value="1" disabled>Vendor1
<input type="checkbox" name="Vendor2" id="Vendor2" value="1" disabled>Vendor2
<input type="checkbox" name="Vendor3" id="Vendor3" value="1" disabled>Vendor3
<input type="checkbox" name="Vendor4" id="Vendor4" value="1" disabled>Vendor4

Questo codice non mi funziona, la stessa cosa la vorrei per le select ma non so dove partire, mi da un input a riguardo. Ringrazio in anticipo.