How to modify existing json structure by merging it with new one

Question

Here i have existing structure like

{
    "name": "Parent",
    "hierarchyNumber": "0",
    "children": [ {
            "name": "ParentC1",
            "hierarchyNumber": "1",
            "children": [ {
                "name": "ParentC1C",
                "hierarchyNumber": "1.1",
                "children": []
            } ]
        }
    ]
}

And i have new structure like:

{
    "name": "Child",
    "hierarchyNumber": "0",
    "children": [ {
            "name": "ChildC1",
            "hierarchyNumber": "1",
            "children": [ {
                "name": "ChildCC1",
                "hierarchyNumber": "1.1",
                "children": []
            } ]
        }
    ]
}

I want to add new structure as child in "ParentC1C" and modify the existing structure hierarchy which should be in order with existing structure like below:

{
    "name": "Parent",
    "hierarchyNumber": "0",
    "children": [ {
        "name": "ParentC1",
        "hierarchyNumber": "1",
        "children": [ {
            "name": "ParentC1C",
            "hierarchyNumber": "1.1",
            "children": [ {
                "name": "Child",
                "hierarchyNumber": "1.1.1",
                "children": [ {
                    "name": "ChildC1",
                    "hierarchyNumber": "1.1.1.1",
                    "children": [ {
                        "name": "ChildCC1",
                        "hierarchyNumber": "1.1.1.1.1",
                        "children": []
                    } ]
                } ]
            } ]
        } ]
    } ]
}

Here i am able to traverse through tree and get the parent element from existing structure and add new structure there with code:

function traverseStructure( root, selectedParentElement ) {
    if( root.children && root.children.length > 0 ) {
        for( var k in root.children ) {
            if( root.children[ k ].Id === selectedParentElement ) {
                return root.children[ k ];
            } else if( root.children.length ) {
                return traverseStructure( root.children[ k ], selectedParentElement );
            }
        }
    }
}

But not able to understand how can i modify Hierarchical level of new structure as expected. Could anyone please help me here.

Answer 1

A bit strange question is there any Id you are checking ??
Made a demo fixing hierarchyNumber while traversing, but child is placed @end.

Anyway there is uncomplete info/definition in question to answer exactly.

function put2lastEmpty(root, child) {
    var hierarchyNumber = root.hierarchyNumber;
    while(true) {
        root = root.children[0]; // in case there is just 1 ??
        if (hierarchyNumber == "0") hierarchyNumber = root.hierarchyNumber;
        else {
            hierarchyNumber += ".1";
            if(root) root.hierarchyNumber = hierarchyNumber
            else break;
        }
        if (!root.children.length && child) {
            root.children.push(child); // add child here
            child = null;
        }
    }
}
var root = root();
put2lastEmpty(root, child())
console.log(JSON.stringify(root,null,2))

function root() { return {
    "name": "Parent",
    "hierarchyNumber": "0",
    "children": [ {
            "name": "ParentC1",
            "hierarchyNumber": "1",
            "children": [ {
                "name": "ParentC1C",
                "hierarchyNumber": "1.1",
                "children": []
            } ]
        }
    ]
};}

function child() { return {
    "name": "Child",
    "hierarchyNumber": "0",
    "children": [ {
            "name": "ChildC1",
            "hierarchyNumber": "1",
            "children": [ {
                "name": "ChildCC1",
                "hierarchyNumber": "1.1",
                "children": []
            } ]
        }
    ]
};}