doubleItrGen.js

function* dfs(node) {
  if (!node) return;
  if (node.type === 'text') {
    for (const ch of node.val) {
      yield ch;
    }
  }

  for (const child of (node.children || [])) {
    yield *dfs(child);
  }
}

function* zip(a, b) {
  while (true) {
    const nextA = a.next(), nextB = b.next();
    if (nextA.done && nextB.done) break;
    yield [nextA.value, nextB.value];
  }
}

const rootA = {
  type: 'text',
  val: 'weed',
  children: [
    {
      val: 245,
    },
    {
      val: 999,
      children: [
        {
          type: 'text',
          val: 'g',
        },
        {
          type: 'text',
          val: 'uy',
        }
      ]
    },
    {
      type: 'text',
      val: 'f',
    }
  ],
};

const rootB = {
  type: 'span',
  children: [
    {
      type: 'text',
      val: 'weed',
    },
    {
      type: 'span',
      children: [
        {
          type: 'text',
          val: 'guy',
        },
        {
          type: 'text',
          val: 'f',
        }
      ]
    }
  ],
};

const match = () => {
  for (const [a, b] of zip(dfs(rootA), dfs(rootB))) {
    if (a !== b) {
      return false;
    }
  }

  return true;
}

console.log(match());