Takes the simplest approach to ensure a page has the libraries you need, or loads 'em from a CDN. Good for use in components, or embedded scripts.

ensure('jquery', function(err){
  if(err) throw err;

  // jQuery is ready, do something with it.
})

ensure('jquery', 'underscore', 'backbone', function(err){
  if(err) throw err;

  // It's all loaded, go for it!
})

Comes with support for:

• AngularJS
• Backbone
• Hammer
• jQuery
• jQuery UI
• Underscore
• WebFont
• Zepto

For libraries not built in, just pass in a function that returns a url string if the script needs to be loaded. (shown in coffeescript)

blam= -> blam ? "//darthapo.github.com/blam.js/blam.min.js"

ensure 'jquery', blam, (err)->
  throw err if err?