Can someone explain to me how this parse function actually works?
function parseFlickrJson(jsonstring){
var data=null;
var jsonFlickrApi=function(d){
data = d;
}
eval(jsonstring);
return data;
}
1 Answer
JSON is actually valid JavaScript. So all you need to 'decode' it, is to evaluate it as JavaScript (hence the eval). It's also using something known as JSONP http://en.wikipedia.org/wiki/JSONP where more than just JSON is returned.
JSONP is basically JSON wrapped in a function call. The content of a JSONP response might be:
parseResponse({"Name": "Cheeso", Id : 1823, "Rank": 7})
What this means is that when you evaluate JSONP, it will attempt to call a function (in this example parseResponse and in your case jsonFlickrApi). This is why the jsonFlickrApi function must be defined before the eval(jsonstring) occurs.
2 Comments
bradley.ayers
the
var jsonFlickrApi = function(d) ... is actually creating an anonymous function and storing a reference to it in jsonFlickrApi (so I suppose it's not really anonymous). eval evaluates a string as if it was source code. Since the response from the Flickr API includes a call to jsonFlickrApi, it's important that that function actually exists, or you'll get an exception.