How to use grep instead of the select and map methods

This section will teach you how to use grep instead of other methods in Ruby, such as select and map, to search through a collection.

To start with, I'm going to create an array of filenames, as shown in the following code:

arr = ['hey.rb', 'there.rb', 'index.html'] 

Now let's see how we can use grep to perform the functions of select or map.

First, let's say you want to return only the files that end in the extension .rb, and along with it, you want to remove the extension so the output has only filenames.

The typical code to implement this type of behavior would be something like this:

p arr.select { |x| x=~ /\.rb/ }.map{ |x| x[0..-4]} 

The output should just have the ["hey", "there"] values.

Though it worked, we can make it more efficient using the grep method...