Find keys of objects in a deeply nested object or array and return references of that objects

findKeyDeep.js

function findKeyDeep(obj, key) {
  const foundKeysReferences = [];
  if (Array.isArray(obj)) {
    obj.forEach(entry =>
      foundKeysReferences.push(...findKeyDeep(entry, key)));
  } else if (typeof obj === 'object' && obj !== null) {
    if (obj[key]) {
      foundKeysReferences.push(obj);
    }
    Object.values(obj).forEach(value =>
      foundKeysReferences.push(...findKeyDeep(value, key)));
  }
  return foundKeysReferences;
};

const obj = [
  {a:{b:{c:{d: 3}}}},
  { e:{ d: 4} }, 
  {f:[[{y:{d:6}}]]}
];
findKeyDeep(o, 'd'); // [{"d":3},{"d":4},{"d":6}]