Too Long; Didn't Read
Reselect is a popular library that provides a convenient way of getting values from a store in a React-Redux application. What makes it so good is its memoization ability. You can read all this in the documentation. In two words, when you use the <em>createSelector()</em> function, it memiozes an output of every input selector and recalculates the resulting value only if any of the input selectors changes its output. The important thing to note here is that reselect uses reference equality (===) to determine a value change.