georgebrock/java_script_helper.rb

## java_script_helper.rb
module JavaScriptHelper

  # Call this in your views to indicate that a feature needs to be initialised
  def use_javascript_for(feature)
    @javascript_features ||= []
    @javascript_features << feature
  end

  # Use this in your layout to add a list of classes to add to the body so that the JavaScript knows which features to initialised
  def javascript_feature_classes
    (@javascript_features || []).uniq.map{ |feature| "with-js-#{feature.downcase}" }.join(" ")
  end

end

## layout.html.erb
<!DOCTYPE HTML>
<html lang="en">
  <head>
    <title>Example layout</title>
    <script type="text/javascript" src="/javascripts/my_site.js"></script>
  </head>
  <body class="<%= javascript_feature_classes %>">
    <%= yield %>
  </body>
</html>

## my_site.js
var MySite = {};

jQuery(function($) {
  for(key in MySite) {
    if(MySite.hasOwnProperty(key)) {
      if(typeof MySite[key]["global_init"] === "function") {
        MySite[key].global_init($);
      }
      if(typeof MySite[key]["init"] === "function" && $("body").hasClass("with-js-" + key.toLowerCase())) {
        MySite[key].init($);
      }
    }
  }
});

MySite.Example = {
  global_init: function($) {
    // Run on all pages
  },
  init: function($) {
    // Run on pages that call use_javascript_for("example")
  }
};

## view.html.erb
<div class="example">
  Some markup that can be enhanced with JavaScript
  <% use_javascript_for("example") %>
</div>
	module JavaScriptHelper

	# Call this in your views to indicate that a feature needs to be initialised
	def use_javascript_for(feature)
	@javascript_features \|\|= []
	@javascript_features << feature
	end

	# Use this in your layout to add a list of classes to add to the body so that the JavaScript knows which features to initialised
	def javascript_feature_classes
	(@javascript_features \|\| []).uniq.map{ \|feature\| "with-js-#{feature.downcase}" }.join(" ")
	end

	end
	<!DOCTYPE HTML>
	<html lang="en">
	<head>
	<title>Example layout</title>
	<script type="text/javascript" src="/javascripts/my_site.js"></script>
	</head>
	<body class="<%= javascript_feature_classes %>">
	<%= yield %>
	</body>
	</html>
	var MySite = {};

	jQuery(function($) {
	for(key in MySite) {
	if(MySite.hasOwnProperty(key)) {
	if(typeof MySite[key]["global_init"] === "function") {
	MySite[key].global_init($);
	}
	if(typeof MySite[key]["init"] === "function" && $("body").hasClass("with-js-" + key.toLowerCase())) {
	MySite[key].init($);
	}
	}
	}
	});

	MySite.Example = {
	global_init: function($) {
	// Run on all pages
	},
	init: function($) {
	// Run on pages that call use_javascript_for("example")
	}
	};
	<div class="example">
	Some markup that can be enhanced with JavaScript
	<% use_javascript_for("example") %>
	</div>