Implementation of a simple Tree data structure - tested with the common DOM structure

simple-tree.js

function createNode(key) {
  const children = [];
  const attributes = {};

  return {
    key,
    children,
    attributes,
    addChild(key) {
      const child = createNode(key);
      children.push(child);
      return child;
    },
    addAttribute(name, value) {
      attributes[name] = value;
    }
  }
}

function createTree(rootKey) {
  const root = createNode(rootKey);
  
  return {
    root,
    addChild(key) {
      return root.addChild(key);
    },
    print() {
      let result = '';
      const traverse = (node, visitFn, depth) => {
        visitFn(node, depth);
        
        if (node.children.length) {
          node.children.forEach(child => {
            traverse(child, visitFn, depth + 1);
          });
        }
      };
      
      const printKeys = (node, depth) => {
        let attributeString =
            result.length === 0 ? '' : Object.keys(node.attributes).reduce((acc, attrName) => {
              return [...acc, `${attrName}=${node.attributes[attrName]}`];
            }, []).join(', ');
        attributeString = !attributeString.length ? '' : `[${attributeString}]`;
        result += result.length === 0 ? node.key : `\n${' '.repeat(depth * 2)}${node.key} ${attributeString}`;
      };
      traverse(root, printKeys, 1);
      return result;
    }
  }
}

const dom = createTree('html');
const head = dom.addChild('head');
const body = dom.addChild('body');

const title = head.addChild('title - Learning Algorithms');
const meta = head.addChild('meta - meta tag');
meta.addAttribute('content-type', 'text/html');
meta.addAttribute('author', 'Victor Igbokwe');

body.addAttribute('bgcolor', 'red');
const main = body.addChild('main');

const h1 = main.addChild('h1 - Learning Algorithms', 'p - Algorithms are methods and patterns in solving problems');
h1.addAttribute('style', 'background-color: red')
const p = main.addChild('p - Algorithms are methods and patterns in solving problems');
const hr = main.addChild('hr');
hr.addAttribute('size', '1');

console.log(dom.print());