// jsr_class.js
  //
  // JSONscriptRequest -- a simple class for making HTTP requests
  // using dynamically generated script tags and JSON
  //
  // Author: Jason Levitt
  // Date: December 7th, 2005
  //
  // A SECURITY WARNING FROM DOUGLAS CROCKFORD:
  // "The dynamic <script> tag hack suffers from a problem. It allows a page 
  // to access data from any server in the web, which is really useful. 
  // Unfortunately, the data is returned in the form of a script. That script 
  // can deliver the data, but it runs with the same authority as scripts on 
  // the base page, so it is able to steal cookies or misuse the authorization 
  // of the user with the server. A rogue script can do destructive things to 
  // the relationship between the user and the base server."
  //
  // So, be extremely cautious in your use of this script.
  //
  //
  // Sample Usage:
  //
  // <script type="text/javascript" src="jsr_class.js"></script>
  // 
  // function callbackfunc(jsonData) {
  //      alert('Latitude = ' + jsonData.ResultSet.Result[0].Latitude + 
  //            '  Longitude = ' + jsonData.ResultSet.Result[0].Longitude);
  //      aObj.removeScriptTag();
  // }
  //
  // request = 'http://api.local.yahoo.com/MapsService/V1/geocode?appid=YahooDemo&
  //            output=json&callback=callbackfunc&location=78704';
  // aObj = new JSONscriptRequest(request);
  // aObj.buildScriptTag();
  // aObj.addScriptTag();
  //
  //
  
  // Constructor -- pass a REST request URL to the constructor
  //
  function JSONscriptRequest(fullUrl) {
      // REST request path
      this.fullUrl = fullUrl; 
      // Keep IE from caching requests
      this.noCacheIE = '&noCacheIE=' + (new Date()).getTime();
      // Get the DOM location to put the script tag
      this.headLoc = document.getElementsByTagName("head").item(0);
      // Generate a unique script tag id
      this.scriptId = 'JscriptId' + JSONscriptRequest.scriptCounter++;
  }
  
  // Static script ID counter
  JSONscriptRequest.scriptCounter = 1;
  
  // buildScriptTag method
  //
  JSONscriptRequest.prototype.buildScriptTag = function () {
  
      // Create the script tag
      this.scriptObj = document.createElement("script");
      
      // Add script object attributes
      this.scriptObj.setAttribute("type", "text/javascript");
      this.scriptObj.setAttribute("charset", "utf-8");
      this.scriptObj.setAttribute("src", this.fullUrl + this.noCacheIE);
      this.scriptObj.setAttribute("id", this.scriptId);
  }
   
  // removeScriptTag method
  // 
  JSONscriptRequest.prototype.removeScriptTag = function () {
      // Destroy the script tag
      this.headLoc.removeChild(this.scriptObj);  
  }
  
  // addScriptTag method
  //
  JSONscriptRequest.prototype.addScriptTag = function () {
      // Create the script tag
      this.headLoc.appendChild(this.scriptObj);
  }