deepGet

Gets the target value in a nested JSON object, based on the keys array.

• Compare the keys you want in the nested JSON object as an Array.
• Use Array.prototype.reduce() to get the values in the nested JSON object one by one.
• If the key exists in the object, return the target value, otherwise return null.

const deepGet = (obj, keys) =>
  keys.reduce(
    (xs, x) => (xs && xs[x] !== null && xs[x] !== undefined ? xs[x] : null),
    obj
  );

let index = 2;
const data = {
  foo: {
    foz: [1, 2, 3],
    bar: {
      baz: ['a', 'b', 'c']
    }
  }
};
deepGet(data, ['foo', 'foz', index]); // get 3
deepGet(data, ['foo', 'bar', 'baz', 8, 'foz']); // null