Question

I have a javascript file from a wordpress plugin that I’m trying to modify. It seems to be getting away with cross-domain requests with some sort of loophole. It’s this function:

function urlCallback(url){
  var req = url;
  var head = document.getElementsByTagName("head").item(0);
  var script = document.createElement("script");
  script.setAttribute("type", "text/javascript");
  script.setAttribute("src", req);
  head.appendChild(script);   
}

The url passed is something like 'http://url.com/page?callback=namespace.myFunction' where myFunction is a function defined elsewhere in the script.

From what I understand, this is inserting a source url at the top of my page, causing the browser to load that page. The callback attached to that url is then called, passing the result as a single parameter to the example function, myFunction.

My problem is that I need to call myFunction for a few different unique urls, but the results are tied to the calling url. myFunction seems to be called whenever the page finishes loading, so I can’t simply keep count of which data set it’s operating on. I need some way for myFunction to either be passed an additional variable encoded in the callback url, or for myFunction to know the url it was attached to.

Can anyone help me?

EDIT:

To elaborate further, here is a simplified version of the code I have:

var parseUrls = (function(){
  function urlCallback(url){
    var req = url;
    // Here is where I need to save the url
    var head = document.getElementsByTagName("head").item(0);
    var script = document.createElement("script");
    script.setAttribute("type", "text/javascript");
    script.setAttribute("src", req);
    head.appendChild(script);   
  }

  return {
    options: {},
    parseNextUrl: function(result) {
        if (!result || !result.data) { return; }
        var data = result.data;
        // Here is where I need the url

    },
    parseUrl: function(result) {
      if (!result || !result.data) { return; }
      var data = result.data;
      for (var i = 0; i < data.length; i++) {
        urlCallback( data[i].url + "/new_url/page?callback=parseUrls.parseNextUrl" );
      }
    },
    showResult: function(options){
      urlCallback( "http://start.url.com/page?callback=parseUrls.parseUrl" );
      this.options = options;
    }
  };
})();

Just to be clear, parseNextUrl is called whenever the source request is finished. Which means all the urlCallback calls have already finished by then.

Answer 1

Here’s the updated code based on the newly provided code.

var parseUrls = (function(){
  function urlCallback(url){
    // Create request
    var head = document.getElementsByTagName("head").item(0);
    var script = document.createElement("script");
    script.setAttribute("type", "text/javascript");
    script.setAttribute("src", req);
    head.appendChild(script);   
  }

  return {
    parsers: [], //response handler array
    options: {},
    parseUrl: function(result) {
      //parseUrls.parseUrl.url = request URL

      if (!result || !result.data) { return; }
      var data = result.data;

      // Create requests
      for (var i = 0; i < data.length; i++) {
        // Create new response handler
        var parseNextUrl = function(result) {
          // parseNextUrl.url = request URL

          if (!result || !result.data) { return; }
          var data = result.data;

          // Check the URL
          console.log('Result URL = ' + parseNextUrl.url);
        };

        // Make callback names and URLs for each handler
        var cbName = "parseUrls.parsers[" + this.parsers.length + "]";
        var req = data[i].url + "/new_url/page?callback=" + encodeURI(cbName);

        // Save the URL in the handler
        parseNextUrl.url = req;

        // Put handler into storage.
        // Note: Don't delete/insert any of parsers array element
        // until no more new requests and all responses are received.
        this.parsers.push(parseNextUrl);

        urlCallback(req);
      }
    },
    showResult: function(options){
      this.parseUrl.url = "http://start.url.com/page?callback=parseUrls.parseUrl";

      urlCallback(this.parseUrl.url);
      this.options = options;
    }
  };
})();