We Keep Coding

Is using XMLHttpRequest() an outdated way to make an Ajax call?

I'm simply using an example from a book I'm reading. The example is labeled, "Loading HTML with Ajax." This is the JS portion of the code:
var xhr = new XMLHttpRequest();
xhr.onload = function() {
if(xhr.status === 200) {
document.getElementById('content').innerHTML = xhr.responseText;
}
};
xhr.open('GET', 'data/data.html', true);
xhr.send(null);
I'm getting the CSS portion of the code (headers, etc.) when I load the page onto the browser but none of the JS (there should be maps which would load onto the page). The example says I should comment out this portion of the code above:
xhr.onload = function() {
if(xhr.status === 200) {
document.getElementById('content').innerHTML = xhr.responseText;
...if I'm running the code locally without a server but that's not working, either.

Is using XMLHttpRequest() an outdated way to make an Ajax call?
Yes, but it still works and that's not the problem. The more modern way is fetch.
I'm getting the CSS portion of the code (headers, etc.) when I load the page onto the browser but none of the JS (there should be maps which would load onto the page).
That's because assigning HTML that contains script tags to innerHTML doesn't run the script defined by those tags. The script tags are effectively ignored.
To run those scripts, you'll need to find them in the result and then recreate them, something along these lines:
var content = document.getElementById('content');
content.innerHTML = xhr.responseText;
content.querySelectorAll("script").forEach(function(script) {
var newScript = document.createElement("script");
newScript.type = script.type;
if (script.src) {
newScript.src = script.src;
} else {
newScript.textContent = script.textContent;
}
document.body.appendChild(newScript);
});
Note that this is not the same as loading the page with script elements in it directly. The code within script tags without async or defer or type="module" is executed immediately when the closing script tag is encountered when loading a page directly (so that the loaded script can use document.write to output to the HTML stream; this is very mid 1990s). Whereas in the above, they're run afterward.
Note that on older browsers, querySelectorAll's NodeList may not have forEach, that was added just a few years ago. See my answer here if you need to polyfill it.

Because I didn't completely understand T.J.'s answer (no offense, T.J.), I wanted to provide a simple answer for anyone who might be reading this. I only recently found this answer on Mozilla.org: How do you set up a local testing server? (https://developer.mozilla.org/en-US/docs/Learn/Common_questions/set_up_a_local_testing_server). I won't go into details, I'll just leave the answer up to Mozilla. (Scroll down the page to the section titled, "Running a simple local HTTP server.")

Firefox addon SDK replace request

I tried to replace by a local script the url of scripts loaded by websites.
I tried to channel.redirectTo() with data.url() and chrome:// (with contentaccessible=yes flag in manifest), but doesn't work, so I compared a regex pattern, if true, it will cancel the XHR GET request.
For example
<script src="http://url/to/script.js"></script>
become
<script src="resource://url/to/new/script.js"></script>
or
<script src="chrome://url/to/new/script.js"></script>
Now I need to replace the url or inject my new script to the page
main.js
var listener = function (event) {
var channel = event.subject.QueryInterface(Ci.nsIHttpChannel);
var match = someFunctionToMatchRegex(channel.URI.spec);
if (match) {
channel.cancel(Cr.NS_BINDING_ABORTED);
}
};
events.on("http-on-modify-request", listener);

I have a redirect module here which is a good example for what you want to do. You might be able to use it, though the module only takes specific urls and not reg expressions at the moment. I'd certainly take a pull request to make this change though.
The code basically just uses redirectTo as you mention, so something else is wrong.

Chrome extension regarding injected script + localstorage

I am puzzling my way through my first 'putting it all together' Chrome extension, I'll describe what I am trying to do and then how I have been going about it with some script excerpts:
I have an options.html page and an options.js script that lets the user set a url in a textfield -- this gets stored using localStorage.
function load_options() {
var repl_adurl = localStorage["repl_adurl"];
default_img.src = repl_adurl;
tf_default_ad.value = repl_adurl;
}
function save_options() {
var tf_ad = document.getElementById("tf_default_ad");
localStorage["repl_adurl"] = tf_ad.value;
}
document.addEventListener('DOMContentLoaded', function () {
document.querySelector('button').addEventListener('click', save_options);
});
document.addEventListener('DOMContentLoaded', load_options );
My contentscript injects a script 'myscript' into the page ( so it can have access to the img elements from the page's html )
var s = document.createElement('script');
s.src = chrome.extension.getURL("myscript.js");
console.log( s.src );
(document.head||document.documentElement).appendChild(s);
s.parentNode.removeChild(s);
myscript.js is supposed to somehow grab the local storage data and that determines how the image elements are manipulated.
I don't have any trouble grabbing the images from the html source, but I cannot seem to access the localStorage data. I realize it must have to do with the two scripts having different environments but I am unsure of how to overcome this issue -- as far as I know I need to have myscript.js injected from contentscript.js because contentscript.js doesn't have access to the html source.
Hopefully somebody here can suggest something I am missing.
Thank you, I appreciate any help you can offer!
-Andy

First of all: You do not need an injected script to access the page's DOM (<img> elements). The DOM is already available to the content script.
Content scripts cannot directly access the localStorage of the extension's process, you need to implement a communication channel between the background page and the content script in order to achieve this. Fortunately, Chrome offers a simple message passing API for this purpose.
I suggest to use the chrome.storage API instead of localStorage. The advantage of chrome.storage is that it's available to content scripts, which allows you to read/set values without a background page. Currently, your code looks quite manageable, so switching from the synchronous localStorage to the asynchronous chrome.storage API is doable.
Regardless of your choice, the content script's code has to read/write the preferences asynchronously:
// Example of preference name, used in the following two content script examples
var key = 'adurl';
// Example using message passing:
chrome.extension.sendMessage({type:'getPref',key:key}, function(result) {
// Do something with result
});
// Example using chrome.storage:
chrome.storage.local.get(key, function(items) {
var result = items[key];
// Do something with result
});
As you can see, there's hardly any difference between the two. However, to get the first to work, you also have to add more logic to the background page:
// Background page
chrome.extension.onMessage.addListener(function(message, sender, sendResponse) {
if (message.type === 'getPref') {
var result = localStorage.getItem(message.key);
sendResponse(result);
}
});
On the other hand, if you want to switch to chrome.storage, the logic in your options page has to be slightly rewritten, because the current code (using localStorage) is synchronous, while chrome.storage is asynchronous:
// Options page
function load_options() {
chrome.storage.local.get('repl_adurl', function(items) {
var repl_adurl = items.repl_adurl;
default_img.src = repl_adurl;
tf_default_ad.value = repl_adurl;
});
}
function save_options() {
var tf_ad = document.getElementById('tf_default_ad');
chrome.storage.local.set({
repl_adurl: tf_ad.value
});
}
Documentation
chrome.storage (method get, method set)
Message passing (note: this page uses chrome.runtime instead chrome.extension. For backwards-compatibility with Chrome 25-, use chrome.extension (example using both))
A simple and practical explanation of synchronous vs asynchronous ft. Chrome extensions

How do I use jQuery in Windows Script Host?

I'm working on some code that needs to parse numerous files that contain fragments of HTML. It seems that jQuery would be very useful for this, but when I try to load jQuery into something like WScript or CScript, it throws an error because of jQuery's many references to the window object.
What practical way is there to use jQuery in code that runs without a browser?
Update: In response to the comments, I have successfully written JavaScript code to read the contents of files using new ActiveXObject('Scripting.FileSystemObject');. I know that ActiveX is evil, but this is just an internal project to get some data out of some files that contain HTML fragments and into a proper database.
Another Update: My code so far looks about like this:
var fileIo, here;
fileIo = new ActiveXObject('Scripting.FileSystemObject');
here = unescape(fileIo.GetParentFolderName(WScript.ScriptFullName) + "\\");
(function() {
var files, thisFile, thisFileName, thisFileText;
for (files = new Enumerator(fileIo.GetFolder(here).files); !files.atEnd(); files.moveNext()) {
thisFileName = files.item().Name;
thisFile = fileIo.OpenTextFile(here + thisFileName);
thisFileText = thisFile.ReadAll();
// I want to do something like this:
s = $(thisFileText).find('input#txtFoo').val();
}
})();
Update: I posted this question on the jQuery forums as well: http://forum.jquery.com/topic/how-to-use-jquery-without-a-browser#14737000003719577

Following along with your code, you could create an instance of IE using Windows Script Host, load your html file in to the instance, append jQuery dynamically to the loaded page, then script from that.
This works in IE8 with XP, but I'm aware of some security issues in Windows 7/IE9. IF you run into problems you could try lowering your security settings.
var fileIo, here, ie;
fileIo = new ActiveXObject('Scripting.FileSystemObject');
here = unescape(fileIo.GetParentFolderName(WScript.ScriptFullName) + "\\");
ie = new ActiveXObject("InternetExplorer.Application");
ie.visible = true
function loadDoc(src) {
var head, script;
ie.Navigate(src);
while(ie.busy){
WScript.sleep(100);
}
head = ie.document.getElementsByTagName("head")[0];
script = ie.document.createElement('script');
script.src = "http://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js";
head.appendChild(script);
return ie.document.parentWindow;
}
(function() {
var files, thisFile, win;
for (files = new Enumerator(fileIo.GetFolder(here).files); !files.atEnd(); files.moveNext()) {
thisFile = files.item();
if(fileIo.GetExtensionName(thisFile)=="htm") {
win = loadDoc(thisFile);
// your jQuery reference = win.$
WScript.echo(thisFile + ": " + win.$('input#txtFoo').val());
}
}
})();

This is pretty easy to do in Node.js with the cheerio package. You can read in arbitrary HTML from whatever source you want, parse it with cheerio and then access the parsed elements using jQuery style selectors.

Parsing XML / RSS from URL using Java Script

Hi i want to parse xml/rss from a live url like http://rss.news.yahoo.com/rss/entertainment using pure Java Script(not jquery). I have googled a lot. Nothing worked for me. can any one help with a working piece of code.

(You cannot have googled a lot.) Once you have worked around the Same Origin Policy, and if the resource is served with an XML MIME type (which it is in this case, text/xml), you can do the following:
var x = new XMLHttpRequest();
x.open("GET", "http://feed.example/", true);
x.onreadystatechange = function () {
if (x.readyState == 4 && x.status == 200)
{
var doc = x.responseXML;
// …
}
};
x.send(null);
(See also AJAX, and the XMLHttpRequest Level 2 specification [Working Draft] for other event-handler properties.)
In essence: No parsing necessary. If you then want to access the XML data, use the standard DOM Level 2+ Core or DOM Level 3 XPath methods, e.g.
/* DOM Level 2 Core */
var title = doc.getElementsByTagName("channel")[0].getElementsByTagName("title")[0].firstChild.nodeValue;
/* DOM Level 3 Core */
var title = doc.getElementsByTagName("channel")[0].getElementsByTagName("title")[0].textContent;
/* DOM Level 3 XPath (not using namespaces) */
var title = doc.evaluate('//channel/title/text()', doc, null, 0, null).iterateNext();
/* DOM Level 3 XPath (using namespaces) */
var namespaceResolver = (function () {
var prefixMap = {
media: "http://search.yahoo.com/mrss/",
ynews: "http://news.yahoo.com/rss/"
};
return function (prefix) {
return prefixMap[prefix] || null;
};
}());
var url = doc.evaluate('//media:content/#url', doc, namespaceResolver, 0, null).iterateNext();
(See also JSX:xpath.js for a convenient, namespace-aware DOM 3 XPath wrapper that does not use jQuery.)
However, if for some (wrong) reason the MIME type is not an XML MIME type, or if it is not recognized by the DOM implementation as such, you can use one of the parsers built into recent browsers to parse the responseText property value. See pradeek's answer for a solution that works in IE/MSXML. The following should work everywhere else:
var parser = new DOMParser();
var doc = parser.parseFromString(x.responseText, "text/xml");
Proceed as described above.
Use feature tests at runtime to determine the correct code branch for a given implementation. The simplest way is:
if (typeof DOMParser != "undefined")
{
var parser = new DOMParser();
// …
}
else if (typeof ActiveXObject != "undefined")
{
var xmlDoc = new ActiveXObject("Microsoft.XMLDOM");
// …
}
See also DOMParser and HTML5: DOM Parsing and Serialization (Working Draft).

One big problem you might run into is that generally, you cannot get data cross domain. This is big issue with most rss feeds.
The common way to deal with loading data in javascript cross domain is calls JSONP. Basically, this means that the data you are retrieving is wrapped in a javascript callback function. You load the url with a script tag, and you define the function in your code. So when the script loads, it executes the function and passes the data to it as an argument.
The problem with most xml/rss feeds is that services that only provide xml tend not to provide JSONP wrapping capability.
Before you go any farther, check to see if your data source provides a json format and JSONP functionality. That will make this a lot easier.
Now, if your data source doesn't provide json and jsonp functionality, you have to get creative.
On relatively easy way to handle this is to use a proxy server. Your proxy runs somewhere under your control, and acts as a middleman to get your data. The server loads your xml, and then your javascript does the requests to it instead. If the proxy server runs on the same domain name then you can just use standard xhr(ajax) requests and you don't have to worry about cross-domain stuff.
Alternatively, your proxy server can wrap the data in a jsonp callback and you can use the method mentioned above.
If you are using jQuery, then xhr and jsonp requests are built-in methods and so make doing the coding very easy. Other common js libraries should also support these. If you are coding all of this from scratch, its a little more work but not terribly difficult.
Now, once you get your data hopefully its just json. Then there's no parsing needed.
However, if you end up having to stick with an xml/rss version, and if you're jQuery, you can simply use jQuery.parseXML http://api.jquery.com/jQuery.parseXML/.

better convert xml to json. http://jsontoxml.utilities-online.info/
after converting if you need to print json object check this tutorial
http://www.w3schools.com/json/json_eval.asp