高阶函数connect

export function createConnect({
  connectHOC = connectAdvanced,
  mapStateToPropsFactories = defaultMapStateToPropsFactories,
  mapDispatchToPropsFactories = defaultMapDispatchToPropsFactories,
  mergePropsFactories = defaultMergePropsFactories,
  selectorFactory = defaultSelectorFactory
} = {}) {
  return function connect(
    mapStateToProps,
    mapDispatchToProps,
    mergeProps,
    {
      pure = true,
      areStatesEqual = strictEqual,
      areOwnPropsEqual = shallowEqual,
      areStatePropsEqual = shallowEqual,
      areMergedPropsEqual = shallowEqual,
      ...extraOptions
    } = {}
  ) {
    const initMapStateToProps = match(
      mapStateToProps,
      mapStateToPropsFactories,
      'mapStateToProps'
    )
    const initMapDispatchToProps = match(
      mapDispatchToProps,
      mapDispatchToPropsFactories,
      'mapDispatchToProps'
    )
    const initMergeProps = match(mergeProps, mergePropsFactories, 'mergeProps')

    return connectHOC(selectorFactory, {
      // used in error messages
      methodName: 'connect',

      // used to compute Connect's displayName from the wrapped component's displayName.
      getDisplayName: name => `Connect(${name})`,

      // if mapStateToProps is falsy, the Connect component doesn't subscribe to store state changes
      shouldHandleStateChanges: Boolean(mapStateToProps),

      // passed through to selectorFactory
      initMapStateToProps,
      initMapDispatchToProps,
      initMergeProps,
      pure,
      areStatesEqual,
      areOwnPropsEqual,
      areStatePropsEqual,
      areMergedPropsEqual,

      // any extra options args can override defaults of connect or connectAdvanced
      ...extraOptions
    })
  }
}

export default /*#__PURE__*/ createConnect()

 

因为 导出的是 

createConnect() 已经带了一个括号，所以只用两个括号就行了