Hands-On Design Patterns with React Native

Using reduce to reimplement filter and map

It's time for a little challenge. Did you know that you can implement both map and filter with reduce?

Before we begin, let's do a quick recap how the filter function works:

How the filter function works on collection

Suppose we have a task collection and want to filter only tasks with type equal to 1, as follows:

const onlyType1 = task => task.type === 1

With a standard filter function, you would simply write the following:

tasks.filter(onlyType1)

But now, imagine there was no filter function and, so far, you only had reduce in your toolbox.

You could do the following:

tasks.reduce((acc,t) =>