Edit in JSFiddle

flag = 1;
function check(id, name)
{        
    if (flag == 0 )
    {
        $( "form#" + id + " input[type='checkbox']" ).attr( 'checked' , false);
        flag = 1;
    }
    else
    {
        $( "form#" + id + " input[type='checkbox']" ).attr( 'checked' , true);
        flag = 0;
    }
    
}

<form action="blablabla" method="post" accept-charset="utf-8" name="filter" id="filter" enctype="multipart/form-data">
<input type="checkbox" name="allbox" value="" onClick="check(filter, filter)"/>check all<br>
<input type="checkbox" name="filter" value="filter1"  />1<br>
<input type="checkbox" name="filter" value="filter2"  />2<br>
<input type="checkbox" name="filter" value="filter3"  />3<br>
</form>