Transformations can also be done in a component's render() method. Some transformations could be calculated in an action creator or reducer, and the transformed data could be kept in the store. In order for your mapStateToProps function to be as fast as possible, you should only re-run these complex transformations when the relevant data has changed. Transforming data can often be expensive ( and usually results in new object references being created). Only Perform Expensive Operations When Data Changes This will also ensure that if the input values haven't changed, mapStateToProps will still return the same result values as before, and connect can skip re-rendering. Put these operations in memoized selector functions to ensure that they only run if the input values have changed. It does not matter if a mapStateToProps function is written using the function keyword ( function mapState(state) If you do not wish to subscribe to the store, pass null or undefined to connect in place of mapStateToProps. This function should be passed as the first argument to connect, and will be called every time when the Redux store state changes. It should take a first argument called state, optionally a second argument called ownProps, and return a plain object containing the data that the connected component needs. To learn React, check out the ( ).Function mapStateToProps ( state, ownProps ? ) However we understand that this tool wouldn't be useful if you couldn't customize it when you are ready for it. The curated feature set is suitable for small and middle deployments, and you shouldn't feel obligated to use this feature. All of the commands except `eject` will still work, but they will point to the copied scripts so you can tweak them. Instead, it will copy all the configuration files and the transitive dependencies (webpack, Babel, ESLint, etc) right into your project so you have full control over them. This command will remove the single build dependency from your project. If you aren't satisfied with the build tool and configuration choices, you can `eject` at any time. 
The build is minified and the filenames include the hashes.\ It correctly bundles React in production mode and optimizes the build for the best performance. See the section about ( ) for more information.īuilds the app for production to the `build` folder.\
Launches the test runner in the interactive watch mode.\ You may also see any lint errors in the console. The page will reload when you make changes.\ This project was bootstrapped with ( ), using the ( ) and ( ) template. # Getting Started with Create React App and Redux
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