Category Tree js

tree.js

class Node{
  constructor(value){
    this.value = value;
    this.children = [];
  }
}

class CategoryTree{
  constructor() {
    this.roots = [];
  }

  addCategory (value, parent) {
    this.addNode(this.roots, value, parent);
  }

  addNode(roots, value, parent) {
    const children = [];
    let added = false;

    roots.forEach(node => {
      if(node.value === parent){
        node.children.push(new Node(value));
        added = true;
      }else{
        node.children.forEach(child => children.push(child))
      }

      if(node.value === value) {
        throw Error(`Category ${value} has already been added`);
      }
    });

    if(!added && children.length > 0) {
      added = this.addNode(children, value, parent);
    }
    
    if(roots == this.roots && parent === null){
      this.roots.push(new Node(value));
    }else if(roots == this.roots && added === false) {
      throw Error(`Parent ${parent} does not exisits`);
    }

    return added
  }

  getChildren(value) {
    const nodes = this.visitNodes(this.roots, value);
    return nodes.map((node) => node.value);
  }

  visitNodes(roots, value) {
    let children = [];

    let subNodes = [];
    roots.forEach(node => {
      if(node.value === value) {
        children = node.children;
      }else {
        node.children.forEach(child => subNodes.push(child))
      }
    });

    if(subNodes.length > 0) {
      children = this.visitNodes(subNodes, value);
    }

    return children;
  }
}


function main() {
  const tree = new CategoryTree();
  tree.addCategory('A', null);
  tree.addCategory('B', 'A');
  tree.addCategory('C', 'A');

  console.log(tree.getChildren('A'));
}

main()