opal_blocks.rb

[1, 2, 3, 4].each do |a|
  a
end

// [1, 2, 3, 4].$each($iter(function(a) { return a }, self));

Array.prototype.$each = function(block) {
  if (typeof(block) === 'function' && block._isBlock) {
    var block = block; 
  }
  else {
    block = nil; 
  }
  
  
};