deepGet.js

// DeepGet
let resp = {
  collection: [
    {
      name: 'batman', 
      metadata: {
        rating: 'PG-14',
        year: 1985
      }
    },
    {
      name: 'joker', 
      metadata: {
        rating: 'PG-14',
        year: 2019
      }
    },
    {
      name: 'toy story', 
      metadata: {
        rating: 'PG-14',
        year: 2000
      }
    }
  ]
};

function deepGet(obj, path) {
  path = Array.isArray(path) ? path : [path];
  let ref = obj;
  for (let key of path) {
    if (key in ref) {
      ref = ref[key];
    } else {
      return undefined;
    }
  }
  
  return ref;
}

console.log(deepGet(resp, 'collection'));
console.log(deepGet(resp, ['collection', 2, 'metadata', 'year']));

// console.log(resp.collection[0].metadata.year);