Unused ownProps parameter of the React Redux mapStateToProps function should be removed

• REACT_REDUX_UNUSED_OWN_PROPS_PARAM
• Code Quality
• Low
• react

This rule applies when the second ownProps parameter of the React Redux mapStateToProps function is not used.

The mapStateToProps(state, ownProps) is specified as the first argument of connect() call and its ownProps parameter receives the props object of the wrapper component. If the ownProps parameter is not present, React Redux skips calling the function at the props change.

Therefore, for performance, it is recommended to remove the ownProps 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 the mapDispatchToProps which takes ownProps parameter in a similar way.

Noncompliant Code Example

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);

Compliant Code Example

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);

Version

This rule was introduced in DeepScan 1.26.0.

See

• mapStateToProps

• mapDispatchToProps

• The Number of Declared Arguments Affects Behavior