How to load XMLHttpRequest?

How do I load a JSON file into my Rails app from Amazon S3 if I have the error that "XMLHttpRequest cannot load X. Origin X is not allowed by Access-Control-Allow-Origin."?

• I am trying to load a JSON file hosted on Amazon S3  into a MustacheJS template in my rails app. But the data is not passing through. The error in the console is XMLHttpRequest cannot load http://dfndrr.s3.amazonaws.com/test/posts.json. Origin http://dfndrr-dev.herokuapp.com is not allowed by Access-Control-Allow-Origin. Here is the file. I am just using this for testing and learning and this is obviously not how I would structure apps long term https://github.com/JGallardo/tutorials/blob/master/ruby/dfndrr-dev/app/views/blog/index.html.erb I have been browsing Google and though I find some answers, I am not sure how to put it all together. For example, this person solved this but in a Sinatra app. I just need to know how to do this in rails. https://gist.github.com/miry/5447203

• Answer:

  The best and easiest way is looking into CORS. Amazon S3 has a guide for setting it up: http://docs.aws.amazon.com/AmazonS3/latest/dev/cors.html. You do lose support for older browsers like IE7, though. If you want a brittle, hack-y, and generally messy solution, you can mimic JSONP. See this: https://forums.aws.amazon.com/message.jspa?messageID=190557 Another (even less preferred) technique would be aliasing S3 under a subdomain (i.e. static.example.com) and using iframes.