Helper method for looking at how Opal turns Ruby code into JS. Runs anywhere coderay is loaded, e.g. pry and `irb -r coderay`

opal_helper.rb

# try options like arity_cheeck: true
def h(opal_code, options={})
  javascript = Opal.compile opal_code, options
  puts CodeRay.highlight(javascript, :javascript, {}, :terminal)
end

Example:

> h "def add(a, b) a + b end; add 1, 2"
/* Generated by Opal 0.5.5 */
(function($opal) {
  var self = $opal.top, $scope = $opal, nil = $opal.nil, $breaker = $opal.breaker, $slice = $opal.slice;
  $opal.add_stubs(['$+', '$add']);
  $opal.Object._proto.$add = function(a, b) {
    var self = this;
    return a['$+'](b);
  };
  return self.$add(1, 2);
})(Opal);
=> nil