js全选checkbox
<input type="checkbox" name="selectall" value=on onclick="selectAll()">
<script>
function selectAll(form) {
    var obj = document.getElementsByName('selectall');
    var cks = document.getElementsByTagName("input");
    var ckslen = cks.length;
    for(var i=0;i<ckslen-1;i++) {
        if(cks[i].type == 'checkbox') {
            cks[i].checked = obj[0].checked;
        }
    }
}
</script>