index.js

var hasOwnProp = Object.prototype.hasOwnProperty;

module.exports = deep;

function deep(obj, path, value) {
  if (arguments.length === 3) return set.apply(null, arguments);
  return get.apply(null, arguments);
}

function get(obj, path) {
  var keys = Array.isArray(path) ? path : path.split(".");
  for (var i = 0; i < keys.length; i++) {
    var key = keys[i];
    if (!obj || !hasOwnProp.call(obj, key)) {
      obj = undefined;
      break;
    }
    obj = obj[key];
  }
  return obj;
}

function set(obj, path, value) {
  obj = Object.create(obj)
  value = Object.freeze(value)
  var keys = Array.isArray(path) ? path : path.split(".");
  for (var i = 0; i < keys.length - 1; i++) {
    var key = keys[i];
    if (deep.p && !hasOwnProp.call(obj, key)) obj[key] = {};
    obj = obj[key];
  }
  obj[keys[i]] = value;
  return value;
}