reduxjs/reselect

Reselect is a JavaScript library that helps you read data from a Redux store without doing unnecessary recalculations. Redux is a popular tool for managing shared application state, and Reselect's job is to make reading that state fast and efficient. The core idea is "memoized selectors." A selector is just a function that reads from the application's state and returns some derived value, for example, filtering a list of tasks to show only the completed ones. Without Reselect, that filtering runs every time anything in the state changes, even if the task list itself didn't change. Reselect remembers the last result and only recalculates when the inputs actually change. This matters in frameworks like React, where unnecessary recalculations can cause the whole UI to re-render. Selectors built with Reselect can also be chained together, the output of one selector feeds into another, so you can build up complex queries from simple building blocks. It is written in TypeScript and already included in Redux Toolkit, the recommended way to use Redux. You would add it when you notice that your Redux-connected components are re-rendering too often, or when you need to derive data (like sorting or filtering) from your stored state in an efficient, reusable way.