UnusedownProps parameter of the React ReduxmapStateToProps function should be removed
This rule applies when the secondownProps parameter of the React ReduxmapStateToProps function is not used.
ThemapStateToProps(state, ownProps) is specified as the first argument ofconnect() call and itsownProps parameter receives the props object of the wrapper component. If theownProps parameter is not present, React Redux skips calling the function at the props change.
Therefore, for performance, it is recommended to remove theownProps parameter if it is not used in the function body. In some cases, such modification saves not only the function execution time but also unnecessary re-renderings.
This rule also applies to themapDispatchToProps which takesownProps parameter in a similar way.
| Noncompliant Code Example | Compliant Code Example | ||
|---|---|---|---|
| 1 | import React from 'react'; | 1 | import React from 'react'; |
| 2 | import { connect } from 'react-redux'; | 2 | import { connect } from 'react-redux'; |
| 3 | 3 | ||
| 4 | function ShowCount(props) { | 4 | function ShowCount(props) { |
| 5 | return <div>count: {props.count}</div>; | 5 | return <div>count: {props.count}</div>; |
| 6 | } | 6 | } |
| 7 | const mapStateToProps = (state, ownProps) => { // REACT_REDUX_UNUSED_OWN_PROPS_PARAM alarm | 7 | const mapStateToProps = (state) => { |
| 8 | return { count: state.count }; | 8 | return { count: state.count }; |
| 9 | } | 9 | } |
| 10 | export default connect(mapStateToProps)(ShowCount); | 10 | export default connect(mapStateToProps)(ShowCount); |
import React from 'react';import { connect } from 'react-redux';function ShowCount(props) { return <div>count: {props.count}</div>;}const mapStateToProps = (state, ownProps) => { // REACT_REDUX_UNUSED_OWN_PROPS_PARAM alarm return { count: state.count };}export default connect(mapStateToProps)(ShowCount);import React from 'react';import { connect } from 'react-redux';function ShowCount(props) { return <div>count: {props.count}</div>;}const mapStateToProps = (state) => { return { count: state.count };}export default connect(mapStateToProps)(ShowCount);This rule was introduced in DeepScan 1.26.0.