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Define Method in JavaScript and Ruby

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In javascript, function can be attached onto any object; object attributes can be anything,when it is a function, it become a method of that object.

If object is prototype of a function, the attached function becomes instance method of that function(`class’).

In ruby, all methods are reside in instance of Class:

  • intance methods are in object.class;
  • singleton methods are in object.eigenclass. in code class << object.in another word, eigenclass;
  • class methods are in eigenclass of object.class, in code object.class.eigenclass
Object#eigenclass
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class Object
  def eigenclass
      class << self;self;end
  end
end

Define singleton method

define singleton method in javascript
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var obj = {};
obj.greeting = function(){
  console.log('hi');
};
define singleton method in ruby
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obj = {}
def obj.greeting1
  puts 'hi'
end

class << obj
  def greeting2
      puts 'hello'
  end
end

Define instance method

define instance method in javascript
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function Clazz(){}
Clazz.prototype.instanceMethod = function(){};
define instance method in ruby
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class Clazz
  def instanceMethod;end
end

Define class method

define class method in javascript
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function Clazz(){}
Clazz.classMethod = function(){};
define class method in ruby
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class Clazz
  define self.classMethod1;end

  class << self
      def classMethod2;end
  end
end

Define attribute

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function Klass(){
  this.name = 'klass'
}
Klass.prototype.attr = 1;

k = new Klass();
k.attr = 123;
k.attr #=> 123
k.name #=> 'klass'
(new Klass()).attr #=> 1
(new Klass()).name #=> 'klass'

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Klass = Class.new
k = Klass.new

k.instance_variable_get(:@attr) #=> nil
k.instance_variable_set(:@attr,123) #=> 123
k.instance_variable_get(:@attr) #=> 123

k.attr #=> undefined method `attr'
def k.attr;@attr;end
k.attr #=> 123

Klass.new.attr #=> undefined method `attr'

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