function _isObject(item: any) {
  return item && typeof item === 'object' && item.constructor === Object
}

// eslint-disable-next-line @typescript-eslint/explicit-module-boundary-types
function mergeDeep(target: any, source: any, extendArray = true) {
  const output =
    target instanceof Date && typeof target.getMonth === 'function'
      ? new Date(target)
      : Object.assign({}, target)
  if (_isObject(target) && _isObject(source)) {
    Object.keys(source).forEach((key) => {
      if (_isObject(source[key])) {
        if (!(key in target)) Object.assign(output, {[key]: source[key]})
        else output[key] = mergeDeep(target[key], source[key], extendArray)
      } else if (Array.isArray(source[key]) && Array.isArray(target[key])) {
        Object.assign(output, {
          [key]: !extendArray
            ? source[key]
            : target[key].concat(source[key].filter((item: any) => !target[key].includes(item))),
        })
      } else {
        Object.assign(output, {[key]: source[key]})
      }
    })
  }
  return output
}

export default mergeDeep