Redux Bad Practices: Duplicate State
Last updated on Nov 15, 2017

Let's say you need to display a filtered list of products.

A bad approach would be to save the filtered list on each filter change in a component's state or in a different key in a Redux store.

onFilterChange(filter) {
  this.setState({
    filteredProducts: this.props.products.filter(...)
  })
}

A good approach would be to use cached selectors with reselect:

mapStateToProps = (state) => ({
  filteredProducts: filteredProductsSelector(state)
})

Or calculate the computed data on render if it's not shared and runs fast:

render() {
  const filteredProducts = this.props.products.filter(...);

  return <div>{ filteredProducts.map(...) }</div>;
}

Redux offers you a mechanism for a single source of truth. If you save different representations of the same data in your store or in component's state you are violating that principal. You should only save raw data once, and calculate everything that can be derived from it.

Back to all articles
We are leading front-end consultancy specializing in React, React Native, and Angular. We build web and mobile apps, train teams and consult on complex projects.

Tel AvivIsrael

New York CityUSA

© 500Tech. Building high-quality software since 2012.