code: function deepMerge (base, custom) {
    Object.keys(custom).forEach(function (key) {
      if (!base.hasOwnProperty(key) || typeof base[key] !== 'object') {
        base[key] = custom[key]
      } else {
        base[key] = deepMerge(base[key], custom[key])
      }
    })
  
    return base
  }
docs: Recusrsively merge config and custom, overriding the base value with custom values