s c h e m a t i c s : c o o k b o o k

function makeReqObj() { return new XMLHttpRequest(); }
  
function httpSendGeneric(method, url, content, errorHandler) {
  try {
    netscape.security.PrivilegeManager.enablePrivilege("UniversalBrowserRead");
  } catch (e) {
    softError("httpSendGeneric",
               e.toString() + " Could not enable UniversalBrowserRead privilege.");
  }

  try {
    var http = makeReqObj();
    if (!http) {
      if (errorHandler) errorHandler("httpSendGeneric", "could not create http object");
      else softError("httpSendGeneric", "could not create http object");
    }
    http.open(method, url, false);
    http.send(content);
    httpCheckOK(http, errorHandler);
    return http;
  } catch (e) {
    if (errorHandler) errorHandler("httpSendGeneric", e.toString());
    else softError("httpSendGeneric", e.toString());
      return null;
  }
}
  
function httpGetGeneric(url, errorHandler) {
  return httpSendGeneric("GET", url, null, errorHandler);
}

function httpPostGeneric(url, content, errorHandler) {
  return httpSendGeneric("POST", url, content, errorHandler);
}

function httpGetGenericK(url, k, errorHandler) {
  var http = makeReqObj();
  http.open("GET", url, true);
  http.onreadystatechange = function () {
    // 4 means loaded
    if (http.readyState == 4) {
      httpCheckOK(http, errorHandler);
      k(http);
    }
  }
}

function softError(callerName, msg) {
  alert(msg);
}
  
function httpCheckOK(http, errorHandler) {
  if (http.status == 200) {
    //alert("looks ok");
    return;
  } else if (errorHandler) {
    errorHandler(http);
  }else {
    softError("http", http.statusText);
  }
}

function httpGetK(url, k, errorHandler) {
  httpGetGenericK(url,
                  function (http) {k(http.responseXML);},
                  errorHandler);
}

function httpGetKText(url, k, errorHandler) {
  httpGetGenericK(url,
                  function (http) {k(http.responseText);},
                  errorHandler);
}

function DOMParseText(str, contentType, errorHandler) {
  try {
    return (new DOMParser()).parseFromString(str, contentType);
  } catch (e) {
    if (errorHandler) errorHandler("DOMParseText", e);
    else softError("DOMParseText", e);
    return null;
  }
}

function httpGetHTML(url,errorHandler) {
  return DOMParseText(httpGetText(url, errorHandler),
                      "text/html", errorHandler);
}

function httpGetXML(url,errorHandler) {
  return DOMParseText(httpGetText(url, errorHandler),
                      "text/xml", errorHandler);
}

function httpGetText(url, errorHandler) {
  return httpGetGeneric(url, errorHandler).responseText;
}

function httpPost(url, content, errorHandler) {
  return httpPostGeneric(url, content, errorHandler).responseXML;
}