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function CascadeCheckmarks(e)
{
// obj gives us the node on which check or uncheck operation has performed
var element = e.srcElement || e.target;
var parentState = true; //default true;
//checking whether obj consists of checkbox to avoid exception
if (isCheckBox(element))
{
var checkedState = element.checked;
//work our way back to the parent <li> element
while (!isListItem(element))
element = element.parentNode;
recurseThroughChildren(element.firstChild, checkedState); //set child nodes to checkedState
//from the <li> work our way back to the parent <ul> element
while (!isList(element))
element = element.parentNode;
recurseThroughParents(element, parentState); //set parent nodes accordingly
}
}
function recurseThroughChildren(element, checkedState)
{
var chkbox;
while(!isNull(element))
{
//mark the child checkbox the same as the parent
chkbox = getCheckBox(element);
if (!isNull(chkbox))
chkbox.checked = checkedState;
//recurse through children of current element
recurseThroughChildren(element.firstChild, checkedState);
element = element.nextSibling;
}
}
function recurseThroughParents(parent, parentState)
{
//if it is an unorderd list, process children
if(isList(parent))
{
//get all child elements that are list items
var item = parent.getElementsByTagName('LI')[0];
var chkbox;
//foreach list item...
while(!isNull(item))
{
//whle the children are not check boxes (only 1 checkbox per list item)
chkbox = getCheckBox(item.firstChild)
if ((!isNull(chkbox)) && (!chkbox.checked))
parentState = false;
item = item.nextSibling;
}
if (!isDiv(parent.parentNode))
{
var parentCheckBox = getCheckBox(parent.parentNode);
if (!isNull(parentCheckBox))
parentCheckBox.checked = parentState;
}
}
if (!isDiv(parent)) //if it is not a div tag countinue to the next parent
recurseThroughParents(parent.parentNode, parentState);
}
//return the first checkbox found
function getCheckBox(obj)
{
var ret = null;
while (!isNull(obj))
{
if (isCheckBox(obj))
ret = obj;
else if (obj.childNodes.length > 0)
ret = getCheckBox(obj.firstChild);
if (isCheckBox(ret))
break;
obj = obj.nextSibling;
}
return ret;
}
//helper functions
function isDiv(obj)
{
if (isNull(obj))
return false;
return (obj.tagName == 'DIV');
}
function isCheckBox(obj)
{
if (isNull(obj))
return false;
return (obj.tagName == 'INPUT' && obj.type == 'checkbox');
}
function isList(obj)
{
if (isNull(obj))
return false;
return (obj.tagName == 'UL');
}
function isListItem(obj)
{
if (isNull(obj))
return false;
return (obj.tagName == 'LI');
}
function isNull(obj)
{
return (obj == null);
}
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