get

Retrieves a set of properties indicated by the given selectors from an object.

• Use Array.prototype.map() for each selector, String.prototype.replace() to replace square brackets with dots.
• Use String.prototype.split('.') to split each selector.
• Use Array.prototype.filter() to remove empty values and Array.prototype.reduce() to get the value indicated by each selector.

const get = (from, ...selectors) =>
  [...selectors].map(s =>
    s
      .replace(/\[([^\[\]]*)\]/g, '.$1.')
      .split('.')
      .filter(t => t !== '')
      .reduce((prev, cur) => prev && prev[cur], from)
  );

const obj = {
  selector: { to: { val: 'val to select' } },
  target: [1, 2, { a: 'test' }],
};
get(obj, 'selector.to.val', 'target[0]', 'target[2].a');
// ['val to select', 1, 'test']