I haven't really written any javascript but am building an iOS application that will utilize JavaScriptCore's framework to read a javascript code to get a variable. What I'm looking to do is set up a GET (I think) so that I can retrieve JSON data from a url and then pull a specific string from the JSON data. Within the GET method, I'll need to add credentials and one parameter. What is the best practice to do this?
As per Rory's statement above the server you are requesting the json data from must either be on the same domain as your Application/Js code or support the CORS headers.
If the above is true, then you can either use JQUery as suggested above, or for a more minimalist approach the W3Schools has a tutorial on basic Ajax.