Lookup by path (IE9+)

lookup.js

'use strict'

function lookup(value, path, defaultVal) {
  defaultVal == null && (defaultVal = null)

  if (value == null) {
    return defaultVal
  }

  if (path === '.' || path === '') {
    path = []
  }

  var keys = Array.isArray(path) ? path : path.split('.')

  for (var i = 0, n = keys.length; i < n; i++) {
    value = value[keys[i]]

    if (value == null) {
      return defaultVal
    }
  }

  return value
}