Parent checkbox selected on selecting child in javascript in asp.net

Sample Treeview 1: On selecting last option in treeview 

 Sample Treeview 2: On selecting child "under 4" its parent checked automatically. 

1) Add the following script 

<script type="text/javascript">
        function OnTreeClick(evt) {
            var src = window.event != window.undefined ? window.event.srcElement : evt.target;
            var isChkBoxClick = (src.tagName.toLowerCase() == "input" && src.type == "checkbox");
            if (isChkBoxClick) {
                var parentTable = GetParentByTagName("table", src);
                var nxtSibling = parentTable.nextSibling;
                //check if nxt sibling is not null & is an element node
                if (nxtSibling && nxtSibling.nodeType == 1) {
                    if (nxtSibling.tagName.toLowerCase() == "div") //if node has children
                    {
                        //check or uncheck children at all levels
                        CheckUncheckChildren(parentTable.nextSibling, src.checked);
                    }
                }
                //check or uncheck parents at all levels
                CheckUncheckParents(src, src.checked);
            }
        }
 
        function CheckUncheckChildren(childContainer, check) {
            var childChkBoxes = childContainer.getElementsByTagName("input");
            var childChkBoxCount = childChkBoxes.length;
            for (var i = 0; i < childChkBoxCount; i++) {
                childChkBoxes[i].checked = check;
            }
        }
 
        function CheckUncheckParents(srcChild, check) {
            var parentTable = GetParentByTagName("table", srcChild);
            var parentDiv = GetParentByTagName("div", srcChild);
            var parentNodeTable = parentDiv.previousSibling;
            if (parentNodeTable) {
                var checkUncheckSwitch;
                if (check) //checkbox checked
                {
                    var isAllSiblingsChecked = AreAllSiblingsChecked(srcChild);
                    if (isAllSiblingsChecked)
                        checkUncheckSwitch = true;
                    else
                        return; //do not need to check parent if any(one or more) child not checked
                }
                else //checkbox unchecked
                {
                    checkUncheckSwitch = false;
                }
 
                var inpElemsInParentTable = parentNodeTable.getElementsByTagName("input");
                var child = parentNodeTable.nextSibling;
 
                var childChkBoxes = child.getElementsByTagName("input");
                var childChkBoxCount = childChkBoxes.length;
                var checkoption = false;
                for (var a = 0; a < childChkBoxCount; a++) {
                    if (childChkBoxes[a].checked == true) {
                        checkoption = true;
                    }
                }
                if (inpElemsInParentTable.length > 0) {
                    var parentNodeChkBox = inpElemsInParentTable[0];
                    parentNodeChkBox.checked = checkoption;
                    //do the same recursively
                    CheckUncheckParents(parentNodeChkBox, checkUncheckSwitch);
                }
            }
        }
 
        function AreAllSiblingsChecked(chkBox) {
            var parentDiv = GetParentByTagName("div", chkBox);
            var childCount = parentDiv.childNodes.length;
            for (var i = 0; i < childCount; i++) {
                if (parentDiv.childNodes[i].nodeType == 1) {
                    //check if the child node is an element node
                    if (parentDiv.childNodes[i].tagName.toLowerCase() == "table") {
                        var prevChkBox = parentDiv.childNodes[i].getElementsByTagName("input")[0];
                        //if any of sibling nodes are not checked, return false
                        //                        if (!prevChkBox.checked) {
                        //                            return false;
                        //                        }
                    }
                }
            }
            return true;
        }
 
        //utility function to get the container of an element by tagname
        function GetParentByTagName(parentTagName, childElementObj) {
            var parent = childElementObj.parentNode;
            while (parent.tagName.toLowerCase() != parentTagName.toLowerCase()) {
                parent = parent.parentNode;
            }
            return parent;
        }
    </script>

2) Add the following code on code behind

 TreeView1.Attributes.Add("onclick", "OnTreeClick(event)");