add javascript page

Author: HundredBillion

en/documentation/ruby-from-other-languages/index.md

@@ -24,6 +24,7 @@ with.
 * [To Ruby From Perl](to-ruby-from-perl/)
 * [To Ruby From PHP](to-ruby-from-php/)
 * [To Ruby From Python](to-ruby-from-python/)
+* [To Ruby From Javascript](to-ruby-from-javascript/)
 
 ## Important Language Features And Some Gotchas
 

en/documentation/ruby-from-other-languages/to-ruby-from-javascript/index.md

@@ -0,0 +1,70 @@
+---
+layout: page
+title: "To Ruby From Javascript"
+lang: en
+---
+
+JavaScript is a ubiquitous programming language, primarily known for web
+development but also used for server-side development with Node.js. Going
+from JavaScript to Ruby, you'll find Ruby has more structured syntax and
+strong object-oriented principles, but you'll also discover Ruby's focus
+on developer happiness and expressiveness.
+
+### Similarities
+
+As with JavaScript, in Ruby,...
+
+* There's an interactive prompt (called `irb`).
+* Objects are dynamically typed.
+* Functions are first-class objects.
+* There are no special line terminators (except the usual newline).
+* You can define functions inside other functions.
+* Arrays and objects (hashes in Ruby) are core data structures.
+* There is excellent support for functional programming with blocks,
+  iterators, and higher-order functions.
+* Variables are dynamically typed—you don't declare their types.
+* Both support closures and can capture variables from their
+  surrounding scope.
+* Regular expressions are built into the language.
+* Both languages are interpreted, not compiled.
+
+
+### Differences
+
+Unlike JavaScript, in Ruby,...
+
+* You don't need to worry about browser compatibility—Ruby runs
+  consistently across platforms.
+* Everything is an object, including numbers and basic types.
+  `5.times { puts "Hello" }` is valid Ruby.
+* There's no concept of `undefined`. Ruby uses `nil` instead of both
+  `null` and `undefined`.
+* Functions are called methods, and you typically call them on objects.
+* There's `public`, `private`, and `protected` for method visibility,
+  rather than relying on conventions or closures for privacy.
+* Ruby has class-based inheritance with single inheritance plus mixins,
+  rather than JavaScript's prototype-based inheritance.
+* Variables have different scopes indicated by their prefix (`@instance`,
+  `@@class`, `$global`) rather than using `var`, `let`, or `const`.
+* String interpolation uses `#{}` syntax: `"Hello #{name}"` instead of
+  template literals or concatenation.
+* Ruby blocks with `do...end` or `{...}` are more powerful than
+  JavaScript arrow functions and are used extensively for iteration.
+* Minimal punctuation: semicolons are optional and rarely used; blocks are delimited with `end` (or `do...end`) rather than `{}`.
+* It's `elsif` instead of `else if`.
+* Ruby has symbols (`:symbol`) which are immutable strings often used
+  as identifiers.
+* No type coercion surprises—Ruby is more predictable about type
+  conversions.
+* Ruby methods can end with `?` (for predicates) or `!` (for
+  destructive operations).
+* Parentheses for method calls are usually optional.
+* You use `require` or `require_relative` instead of `import` or
+  `require()`.
+* Classes are defined with `class...end` blocks rather than constructor
+  functions or class expressions.
+* Ruby has built-in support for operator overloading.
+* When tested for truth, only `false` and `nil` are falsy. Everything
+  else is truthy (including `0`, `""`, and `[]`).
+* Ruby has extensive metaprogramming capabilities—you can easily
+  modify classes and objects at runtime.