A small function to find the sum of levels on a tree and return the level with the largest sum.

findLargestLevelOfTree.js

const findLargestLevel = function(node) {
  // Search Breadth First
  // Define queue
  let queue = [];
  // Enqueue first
  let depth = 0;
  queue.push({node, depth});
  // Track Depth Sums
  let sumTracker = [];
  while (queue.length > 0) {
    let { node, depth } = queue.shift();
    // Queue Children
    for (let i = 0; i < node.children.length; i++) {
      queue.push({ 
        'node': node.children[i],
        'depth': depth + 1,  
      });
    }
    // Add to sumTracker to keep count
    if (typeof sumTracker[depth] !== 'undefined') {
      sumTracker[depth] = sumTracker[depth] + node.value;
    } else {
      sumTracker[depth] = node.value;
    }
  }

  let currentLargestLevel = {};
  // Find largest level by iterating backwards
  for (let i = sumTracker.length - 1; i >= 0; i--) {
    if (i === sumTracker.length - 1 || sumTracker[i] >= currentLargestLevel.sum) {
      currentLargestLevel = {
        'sum': sumTracker[i],
        'depth': i,
      }
    }
  }

  return currentLargestLevel;
};

//
// Tests
//

// Build test tree

let nodeTwo3 = {
  value: 10,
  children: [

  ]
}
let nodeTwo2 = {
  value: 10,
  children: [

  ]
}
let nodeTwo1 = {
  value: 10,
  children: [

  ]
}

let nodeOne2 = {
  value: 10,
  children: [
    nodeTwo1,
    nodeTwo2,
  ]
}
let nodeOne1 = {
  value: 10,
  children: [
    nodeTwo3,
  ]
}

let root = {
  value: 10,
  children: [nodeOne1, nodeOne2]
}


console.log('level two should equal 30 and be largest:', findLargestLevel(root));

nodeOne1.value = 25;
nodeOne2.value = 25;
console.log('level one should equal 50 and be largest:', findLargestLevel(root));

root.value = 100;
console.log('level 0 should equal 100 and be largest:', findLargestLevel(root));