createSelectorselectTodos

createSelectorselectTodos is a naming pattern encountered in Redux applications that use the Reselect library to build memoized selectors for todo data. The idea behind this pattern is to create a specialized selector that derives a value from the todos portion of the state, often in combination with other related state such as a filter or search query. By composing input selectors with a derived result function, the resulting selector computes complex data only when its inputs change, improving performance in large lists.

In practice, a selector built with this pattern typically uses one or more input selectors to extract slices of state, such as the todos array and a visibility filter. The output function then computes a derived value, for example a filtered list of todos or a set of summary metrics. Because the selector is memoized, it returns a cached result if the inputs remain unchanged, avoiding unnecessary recomputation and re-rendering in connected components.

Common derived data include:

- filteredTodos based on a visibility filter (all, active, completed)

- counts or statistics such as total, completed, and active counts

- flags like isEveryCompleted or hasTodos

Benefits of this approach include improved performance, clearer separation of data selection and presentation, and stable references for React components. Potential pitfalls involve ensuring input selectors are pure and return stable data types, avoiding non-serializable inputs, and carefully managing dependent state to prevent stale results. In many codebases, the pattern is implemented with a descriptive name such as selectVisibleTodos or selectTodoStatistics; createSelectorselectTodos represents a variant focused on deriving data from the todos slice.