byau/ruby-vs-js-array-methods

Ruby Array Methods (versus JavaScript)

Instructions

Fork, clone, branch (training), npm install, and bundle install.

Objectives

By the end of this lesson, students should be able to:

• Contrast enumerable methods on Ruby’s Array with iteration methods on JavaScript’s Array.prototype.
• Pass inline code as blocks or reference them as symbols in Ruby and contrast with passing inline code as anonymous or named functions in JavaScript.

Introduction

We'll contrast Ruby's Array methods with JavaScript's.

First let's quickly compare the list of methods for Array in each language.

Ruby Array enumerable methods versus JavaScript Array iteration methods.

Demo

Ruby and JavaScript Arrays both have a map and reduce method. Let's explore using them to see the similarities and differences.

[1] pry(main)> fibs = [0, 1, 1, 2, 3, 5, 8, 13, 21, 34]

> let fibs = [0, 1, 1, 2, 3, 5, 8, 13, 21, 34];

In JavaScript, we use a function to control the behavior of Array methods. In Ruby, we use a block ( {|p|} for one line blocks, do ... end for multi-line blocks).

Lab

Alternating between Ruby and JavaScript, write scripts, in bin/fibonacci.rb and bin/fibonacci.js that:

• calculates the sum of the first ten Fibonacci numbers
• calculates the product of the first ten Fibonacci numbers
• calculates the sum of the the odd Fibonacci numbers
• calculates the product of the even Fibonacci numbers (excluding zero).

Code along

Let's use the scripts bin/people-array.js and bin/people-array.rb to explore Array methods in both Ruby and JavaScript. The data in the objects we'll be processing comes from the comma separated values (CSV) file data/people.csv

The Person objects we'll test against have properties/methods that align with the headers in data/people.csv plus the method age

Lab

Use the bin/people-array.* scripts to

• Count all the people who are older than you (or just pick an age). Younger.
• Count all the people whose first name and last name start with the same letter.
• Calculate the average age of all the people.

Code along

Let's implement normalize_words, unique_words, word_count, and word_frequencies in lib/string.rb

Lab

Build a table mapping Ruby Array methods to direct or modified invocations of JavaScript Array methods. Show the invocation, on an array variable named a, with an example block or function. For the JavaScript equivalent of Ruby Array's +, use an array variable named b.

Ruby	JavaScript
<method>	every
<method>	filter
<method>	find
map	map
reduce	reduce
<method>	some
+	<method>

What do you notice?

Additional Ruby Array Methods

The results of the Ruby Array methods -, &, |, and flatten aren't easily reproducible in JavaScript.

Code along

We'll explore these methods using bin/sets-etc.rb.

License

Source code distributed under the MIT license. Text and other assets copyright General Assembly, Inc., all rights reserved.