In functional programming, being able to reduce is one of the fundamental concepts. Reduce is used to iterate through the values in an array and condense all of the values into a single value. Usually the value is a sum of all of the elements.

Normally, you would want to use a reduce method when you want to sum all of the values in an array and then use the total for some operation. For example, it might make sense to use a reducer when you want to get the total number of items in a shopping cart and determine the tax or determine how many items a customer purchased. Continue reading →