Contrasting prototypal inheritance in JavaScript with classical inheritance in Ruby. In this gist you'll find a JavaScript file and a Ruby file which try to do the same thing, the outputs of each file, and a diff of the two outputs.

inheritance-demo.js

var inspect = require('util').inspect, // To help with printing to console
    log = console.log;

// Define class Foo
function Foo () {
    this.a = [];
}

// Define class Bar which inherits from Foo
function Bar () {}
Bar.prototype = new Foo();
Bar.prototype.constructor = Bar;

// Create instances of Bar
var baz = new Bar(),
    qux = new Bar();

log("New Objects:");
log('  baz.a = %s', inspect(baz.a));
log('  qux.a = %s', inspect(qux.a));

// Push a value onto baz.a
baz.a.push(1);

log("After pushing 1 onto baz.a:");
log('  baz.a = %s', inspect(baz.a));
log('  qux.a = %s', inspect(qux.a));

// Directly define baz.a
baz.a = [1,2,3];

log("After directly defining baz.a as [1,2,3]:");
log('  baz.a = %s', inspect(baz.a));
log('  qux.a = %s', inspect(qux.a));

// Remove baz.a
delete baz.a;

log("After removing a from baz:");
log('  baz.a = %s', inspect(baz.a));
log('  qux.a = %s', inspect(qux.a));

inheritance-demo.rb

# Define class Foo
class Foo
  attr_accessor :a
  def initialize
    @a = []
  end
end

# Define class Bar which inherits from Foo
class Bar < Foo
end

# Create instances of Bar
baz = Bar.new
qux = Bar.new

puts "New Objects:"
puts "  baz.a = #{ baz.a }"
puts "  qux.a = #{ qux.a }"

# Push a value onto baz.a
baz.a.push 1

puts "After pushing 1 onto baz.a:"
puts "  baz.a = #{ baz.a }"
puts "  qux.a = #{ qux.a }"

# Directly define baz.a
baz.a = [1,2,3]

puts "After directly defining baz.a as [1,2,3]:"
puts "  baz.a = #{ baz.a }"
puts "  qux.a = #{ qux.a }"

# Remove baz.a
baz.send :remove_instance_variable, :@a

puts "After removing a from baz:"
puts "  baz.a = #{ baz.a }"
puts "  qux.a = #{ qux.a }"

javascript-output.txt

New Objects:
  baz.a = []
  qux.a = []
After pushing 1 onto baz.a:
  baz.a = [1]
  qux.a = [1]
After directly defining baz.a as [1,2,3]:
  baz.a = [1, 2, 3]
  qux.a = [1]
After removing a from baz:
  baz.a = [1]
  qux.a = [1]

ruby-output.txt

New Objects:
  baz.a = []
  qux.a = []
After pushing 1 onto baz.a:
  baz.a = [1]
  qux.a = []
After directly defining baz.a as [1,2,3]:
  baz.a = [1, 2, 3]
  qux.a = []
After removing a from baz:
  baz.a = nil
  qux.a = []

ruby-vs-javascript.diff

---  ruby-output.txt
+++  javascript-output.txt
 New Objects:
   baz.a = []
   qux.a = []
 After pushing 1 onto baz.a:
   baz.a = [1]
+  qux.a = [1]
-  qux.a = []
 After directly defining baz.a as [1,2,3]:
   baz.a = [1, 2, 3]
+  qux.a = [1]
-  qux.a = []
 After removing a from baz:
+  baz.a = [1]
+  qux.a = [1]
-  baz.a = nil
-  qux.a = []