Creating hierarchical TreeNode structure in TypeScript

Question

Creating hierarchical TreeNode structure in TypeScript

As I work with a flat one-dimensional array of type TreeNode (view interface definition below), my goal is to recursively traverse the array and add subsequent array elements as children.

While attempting a non-recursive approach using a buffer, I encountered an issue when trying to handle

node.children[0].children[0]...children[0]

since each parent has only one child.

    Childify(results: TreeNode[]): any {
    var node: TreeNode;
    var buffer: TreeNode;
    var count: number = 0;

    for (var res of results) {
        if (count == 0) {
            node = res[0];
            buffer = res[0];
            buffer.children = [];
            node.children = [];
        } else if (count == 1) {
            buffer.children = res[0];
        } else {
            node = buffer;
            node.children = [];
            node.children.push(res[0]);
            buffer = <TreeNode>node.children;
        }

        count++;
    }
}

Interface definition:

export interface TreeNode {
label?: string;
data?: any;
icon?: any;
expandedIcon?: any;
collapsedIcon?: any;
children?: TreeNode[];  <---------------
leaf?: boolean;
expanded?: boolean;
type?: string;
parent?: TreeNode;
partialSelected?: boolean;
styleClass?: string;
draggable?: boolean;
droppable?: boolean;
selectable?: boolean;

}

The input:

TreeNode[] = [treeNode1, treeNode2, treeNode3, treeNode4,...,treeNodeX]

The output will be a nested TreeNode object, structured by the children property (which is also of TreeNode type):

TreeNode = treeNode1
treeNode1.children = treeNode2
treeNode2.children = treeNode3
treeNode3.children = treeNode4
treeNodeX-1.children = treeNodeX

I am seeking a method to dynamically access treeNode1.children[0].children[0]......children[0] in a loop for X number of children to assign to the next level of children in treeNode1.

arrays typescript recursion primeng

Answer 1

Answer №1

While I may not have experience with TypeScript, I can offer a solution using JavaScript:

const elements = [ new Element("element1"),
                   new Element("element2"),
                   new Element("element3"),
                   new Element("element4"),
                   new Element("element5")
                 ];

const result = elements.reduceRight((child, parent) => {
    parent.children.push(child);
    return parent;
});

console.log(result);

function Element(name) {
    this.name = name;
    this.children = [];
}

I hope this approach proves helpful for your needs.

Answer 2

While I may not have experience with TypeScript, I can offer a solution using JavaScript:

const elements = [ new Element("element1"),
                   new Element("element2"),
                   new Element("element3"),
                   new Element("element4"),
                   new Element("element5")
                 ];

const result = elements.reduceRight((child, parent) => {
    parent.children.push(child);
    return parent;
});

console.log(result);

function Element(name) {
    this.name = name;
    this.children = [];
}

I hope this approach proves helpful for your needs.

Answer 3

Answer №2

I have created a customized algorithm just for you using simple javascript, which can easily be adapted to match your typescript interface.

Below is the code snippet for the algorithm:

var flatNodes = [
    {
        name: 'node1',
        children: []
    },
    {
        name: 'node2',
        children: []
    },
    {
        name: 'node3',
        children: []
    },
    {
        name: 'node4',
        children: []
    },
    {
        name: 'node5',
        children: []
    }
];

function linkNodes(flatNodes) {
    flatNodes = flatNodes.slice(); //creating a copy of the list

    flatNodes = flatNodes.reverse();

    for (var i = 1; i < flatNodes.length; i++) {
        var previousNode = flatNodes[i - 1];
        var currentNode = flatNodes[i];

        currentNode.children.push(previousNode);
    }

    return flatNodes[flatNodes.length - 1];
}

console.log(linkNodes(flatNodes));

You can see the output of the algorithm below:

{
    "name": "node1",
    "children": [
        {
            "name": "node2",
            "children": [
                {
                    "name": "node3",
                    "children": [
                        {
                            "name": "node4",
                            "children": [
                                {
                                    "name": "node5",
                                    "children": []
                                }
                            ]
                        }
                    ]
                }
            ]
        }
    ]
}

Answer 4

I have created a customized algorithm just for you using simple javascript, which can easily be adapted to match your typescript interface.

Below is the code snippet for the algorithm:

var flatNodes = [
    {
        name: 'node1',
        children: []
    },
    {
        name: 'node2',
        children: []
    },
    {
        name: 'node3',
        children: []
    },
    {
        name: 'node4',
        children: []
    },
    {
        name: 'node5',
        children: []
    }
];

function linkNodes(flatNodes) {
    flatNodes = flatNodes.slice(); //creating a copy of the list

    flatNodes = flatNodes.reverse();

    for (var i = 1; i < flatNodes.length; i++) {
        var previousNode = flatNodes[i - 1];
        var currentNode = flatNodes[i];

        currentNode.children.push(previousNode);
    }

    return flatNodes[flatNodes.length - 1];
}

console.log(linkNodes(flatNodes));

You can see the output of the algorithm below:

{
    "name": "node1",
    "children": [
        {
            "name": "node2",
            "children": [
                {
                    "name": "node3",
                    "children": [
                        {
                            "name": "node4",
                            "children": [
                                {
                                    "name": "node5",
                                    "children": []
                                }
                            ]
                        }
                    ]
                }
            ]
        }
    ]
}

Creating hierarchical TreeNode structure in TypeScript

Answer №1

Answer №2

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