Javascript XML reading problem - javascript

I'm having problems reading an XML local input. The weird thing is that this code works perfectly when the XML is located on a server(This is desktop, by the way, so no SOP problems). I can't figure this out for the life of me, and I've been staring at it, trying different things for a couple of hours.
And another question: does the XML document need a css sheet to be properly read? I would imagine that it doesn't, but I don't know too much about it.
function verify()
{
zipObj = new ActiveXObject("Msxml2.XMLHTTP");
zipObj.open("GET", "KMSY.xml", false);
zipObj.onreadystatechange = function() {
if (zipObj.readyState === 4) {
zipXML = zipObj.responseXML;
read(zipXML);
}
else {
document.getElementById("notice").innerHTML = zipObj.readyState;
}
}
zipObj.send();
}
function read(zipXML)
{
var temp = zipXML.getElementsByTagName("temp_f")[0].childNodes[0].nodeValue;
document.getElementById("notice").innerHTML = temp;
}

Import the XML file to a local server, AJAX obviously needs the XML files to be on web server in order to parse them, or so my humble experience tells me.
You might also want to add the compatibility code for other XML requests into your code.
new XMLHttpRequest() for all browser and IE 8+
new ActiveXObject("Microsoft.XMLHTTP") IE prior to 8

Related

JavaScript: Writing an output file within a limited & secure scenario

I would like to add a function in my javascript to write to a text file in the local directory where the javascript file is located. This means I'm not looking for some insecure way of accessing the user's file system in any way. All I care about is extracting the user's input into an html page that is accessed by my javascript then using that input as data externally. I just need a simple text file. This user input isn't actually text by the way, but rather a bunch of actions using my online game's components that the underlying javascript turns into a text string (so this particular string is what I want to save, not really even anything direct from the user).
I don't want to write to a user's file system, but rather, the file where the javascript (and html) code is located (a folder hosted on a server). Is there any simple way to get some file I/O going?
I know Javascript has a FileReader, is there any way to get it to do this in reverse? Like a FileWriter. GoogleClosure looks like it has a FileWriter, but it doesn't seem to quite work and I can't find any decent examples of how to get it to do this.
If this requires a different language, is there any way I can just get the relevant snippet and insert this into my Javascript file?
(the folder is hosted on a Linux system if that helps)
ADDENDUM: Elias Van Ootegem's solution below is excellent and I would highly recommend looking into it as it's a great example of client-server interaction and getting your system to provide you the data you're looking to extract. Workers are pretty interesting.
But for those of you looking at this post with that similar question that I initially had about JavaScript I/O, I found one other work-a-round depending on your case. My team's project site made use of a database site, MongoDB, that stored some of the user's interaction data if the user had hit a "Save" button. MongoDB, and other online database systems, provide a "dumping" function/script that you can call from your local machine/server and put that data into an output file (I was able to put the JSON data into a text file). From that output, you can write a parser to extract and format the data you desire from that output since databases like MongoDB can be pretty clear as to what format the text will be in (very structured, organized). I wrote a parser in C (with a few libraries I had written to extend the language) to do what I needed, but the idea is pretty generalizable to other programming/scripting languages.
I did look at leaving cookies as option as well, and made use of a test program to try it out (it works too!). However, one tradeoff for leaving cookies on a user's local system is that those cookies generally are meant to hold small amounts of data (usually things like username, date created, & expiration date of the cookie) and are dependent upon the user's local machine. Further, while you can extract the data in those cookies from JavaScript, you are back to the initial problem: the data still exists on the web, not on an output file on your server's file system. In the case you need to extract data and want some guarantee this data will exist on your machine, use Elias Van Ootegem's solution.
JavaScript code that is running client-side cannot access the server's filesystem at the same time, let alone write a file. People often say that, if JS were to have IO capabilities, that would be rather insecure... just imagine how dangerous that would be.
What you could do, is simply build your string, using a Worker that, on closing, returns the full data-string, which is then sent to the server (AJAX call).
The server-side script (Perl, PHP, .NET, Ruby...) can receive this data, parse it and then write the file to disk as you want it to.
All in all, not very hard, but quite an interesting project anyway. Oh, and when using a worker, seeing as it's an online game and everything, perhaps a setInterval to send (a part of) the data every 5000ms might not be a bad idea, either.
As requested - some basic code snippets.
A simple AJAX-setup function:
function getAjax(url,method, callback)
{
var ret;
method = method || 'POST';
url = url || 'default.php';
callback = callback || success;//assuming you have a default function called "success"
try
{
ret = new XMLHttpRequest();
}
catch (error)
{
try
{
ret= new ActiveXObject('Msxml2.XMLHTTP');
}
catch(error)
{
try
{
ret= new ActiveXObject('Microsoft.XMLHTTP');
}
catch(error)
{
throw new Error('no Ajax support?');
}
}
}
ret.open(method, url, true);
ret.setRequestHeader('X-Requested-With', 'XMLHttpRequest');
ret.setRequestHeader('Content-type', 'application/x-www-form-urlencode');
ret.onreadystatechange = callback;
return ret;
}
var getRequest = getAjax('script.php?some=Get&params=inURL', 'GET');
getRequest.send(null);
var postRequest = getAjax('script.php', 'POST', function()
{//passing anonymous function here, but this could just as well have been a named function reference, obviously...
if (this.readyState === 4 && this.status === 200)
{
console.log('Post request complete, answer was: ' + this.response);
}
});
postRequest.send('foo=bar');//set different headers to pos JSON.stringified data
Here's a good place to read up on whatever you don't get from the code above. This is, pretty much a copy-paste bit of code, but if you find yourself wanting to learn just a bit more, Here's a great place to do just that.
WebWorkers
Now these are pretty new, so using them does mean not being able to support older browsers (you could support them by using the event listeners to send each morsel of data to the server, but a worker allows you to bundle, pre-process and structure the data without blocking the "normal" flow of your script. Workers are often presented as a means to sort-of multi-thread JavaScript code. Here's a good intro to them
Basically, you'll need to add something like this to your script:
var worker = new Worker('preprocess.js');//or whatever you've called the worker
worker.addEventListener('message', function(e)
{
var xhr = getAjax('script.php', 'post');//using default callback
xhr.send('data=' + e.data);
//worker.postMessage(null);//clear state
}, false);
Your worker, then, could start off like so:
var time, txt = '';
//entry point:
onmessage = function(e)
{
if (e.data === null)
{
clearInterval(time);
txt = '';
return;
}
if (txt === '' && !time)
{
time = setInterval(function()
{
postMessage(txt);
}, 5000);//set postMessage to be called every 5 seconds
}
txt += e.data;//add new text to current string...
}
Server-side, things couldn't be easier:
if ($_POST && $_POST['data'])
{
$file = $_SESSION['filename'] ? $_SESSION['filename'] : 'File'.session_id();
$fh = fopen($file, 'a+');
fwrite($fh, $_POST['data']);
fclose($fh);
}
echo 'ok';
Now all of this code is a bit crude, and most if it cannot be used in its current form, but it should be enough to get you started. If you don't know what something is, google it.
But do keep in mind that, when it comes to JS, MDN is easily the best reference out there, and as far as PHP goes, their own site (php.net/{functionName}) is pretty ugly, but does contain a lot of info, too...

Setting a javascript variable to an external markdown file

I have a long markdown file. I also have a javascript file that runs a parser over markdown. In my javascript file I have set:
var text = "md/markdown.md"
This does not seem to pull in the content of the markdown file as I would like it to. However, if I copy and paste the contents of the markdown file into the variable, then everything works as it should. Is there a way I can set this javascript variable to pick up the contents of this external markdown file?
In the context of a web browser, if you want JavaScript to fetch data from a URI then you will generally use the XMLHttpRequest object. MDN has a decent tutorial about using XMLHttpRequest.
Most of the general purpose JavaScript libraries include wrappers for XHR that include compatibility fixes (especially for old-IE). I'm fond of YUI. Another option is the relatively ubiquitous jQuery.
It isn't a problem for the case given in the question, but beware of the same origin policy.
Run an AJAX request:
var ajaxRequest, text;
try{
// Opera 8.0+, Firefox, Safari
ajaxRequest = new XMLHttpRequest();
} catch (e){
// Internet Explorer Browsers
try{
ajaxRequest = new ActiveXObject("Msxml2.XMLHTTP");
} catch (e) {
try{
ajaxRequest = new ActiveXObject("Microsoft.XMLHTTP");
} catch (e){
// Something went wrong
alert("Your browser broke!");
return false;
}
}
}
ajaxRequest.onreadystatechange = function(){
if(ajaxRequest.readyState == 4){
text = ajaxRequest.responseText;
}
}
Javascript cannot directly read local files for security reason. As an alternative way, you can take use of XMLHttpRequest to achieve it. Please check the link on the stackoverflow: read external file with Javascript. In addition, HTML5 provides a standard way to interact with local files, via the File API specification. You may refer to the tutorial: http://www.html5rocks.com/en/tutorials/file/filesystem/

reading server file with javascript

I have a html page using javascript that gives the user the option to read and use his own text files from his PC. But I want to have an example file on the server that the user can open via a click on a button.
I have no idea what is the best way to open a server file. I googled a bit. (I'm new to html and javascript, so maybe my understanding of the following is incorrect!). I found that javascript is client based and it is not very straightforward to open a server file. It looks like it is easiest to use an iframe (?).
So I'm trying (first test is simply to open it onload of the webpage) the following. With kgr.bss on the same directory on the server as my html page:
<IFRAME SRC="kgr.bss" ID="myframe" onLoad="readFile();"> </IFRAME>
and (with file_inhoud, lines defined elsewhere)
function readFile() {
func="readFile=";
debug2("0");
var x=document.getElementById("myframe");
debug2("1");
var doc = x.contentDocument ? x.contentDocument : (x.contentWindow.document || x.document);
debug2("1a"+doc);
var file_inhoud=doc.document.body;
debug2("2:");
lines = file_inhoud.split("\n");
debug2("3");
fileloaded();
debug2("4");
}
Debug function shows:
readFile=0//readFile=1//readFile=1a[object HTMLDocument]//
So statement that stops the program is:
var file_inhoud=doc.document.body;
What is wrong? What is correct (or best) way to read this file?
Note: I see that the file is read and displayed in the frame.
Thanks!
Your best bet, since the file is on your server is to retrieve it via "ajax". This stands for Asynchronous JavaScript And XML, but the XML part is completely optional, it can be used with all sorts of content types (including plain text). (For that matter, the asynchronous part is optional as well, but it's best to stick with that.)
Here's a basic example of requesting text file data using ajax:
function getFileFromServer(url, doneCallback) {
var xhr;
xhr = new XMLHttpRequest();
xhr.onreadystatechange = handleStateChange;
xhr.open("GET", url, true);
xhr.send();
function handleStateChange() {
if (xhr.readyState === 4) {
doneCallback(xhr.status == 200 ? xhr.responseText : null);
}
}
}
You'd call that like this:
getFileFromServer("path/to/file", function(text) {
if (text === null) {
// An error occurred
}
else {
// `text` is the file text
}
});
However, the above is somewhat simplified. It would work with modern browsers, but not some older ones, where you have to work around some issues.
Update: You said in a comment below that you're using jQuery. If so, you can use its ajax function and get the benefit of jQuery's workarounds for some browser inconsistencies:
$.ajax({
type: "GET",
url: "path/to/file",
success: function(text) {
// `text` is the file text
},
error: function() {
// An error occurred
}
});
Side note:
I found that javascript is client based...
No. This is a myth. JavaScript is just a programming language. It can be used in browsers, on servers, on your workstation, etc. In fact, JavaScript was originally developed for server-side use.
These days, the most common use (and your use-case) is indeed in web browsers, client-side, but JavaScript is not limited to the client in the general case. And it's having a major resurgence on the server and elsewhere, in fact.
The usual way to retrieve a text file (or any other server side resource) is to use AJAX. Here is an example of how you could alert the contents of a text file:
var xhr;
if (window.XMLHttpRequest) {
xhr = new XMLHttpRequest();
} else if (window.ActiveXObject) {
xhr = new ActiveXObject("Microsoft.XMLHTTP");
}
xhr.onreadystatechange = function(){alert(xhr.responseText);};
xhr.open("GET","kgr.bss"); //assuming kgr.bss is plaintext
xhr.send();
The problem with your ultimate goal however is that it has traditionally not been possible to use javascript to access the client file system. However, the new HTML5 file API is changing this. You can read up on it here.

Reading XML File, Run Correct At IE but Not At Firefox

I make program to read xml file by using traditional JavaScript.
<script type="text/javascript">
var xmlDoc;
function loadxml(sImportXML) {
if( window.ActiveXObject && /Win/.test(navigator.userAgent) ) {
xmlDoc = new ActiveXObject("Msxml.DOMDocument");
xmlDoc.async = false;
xmlDoc.onreadystatechange = function () {
if (xmlDoc.readyState == 4) readXML();
}
xmlDoc.load(sImportXML);
}
else if( document.implementation && document.implementation.createDocument ) {
xmlDoc = document.implementation.createDocument("","",null);
xmlDoc.async=false;
alert(sImportXML);
var loaded = xmlDoc.load(sImportXML);
if (loaded) {
readXML();
}
}
else {
alert("Your browser can\'t handle this script");
return;
}
}
 
<body onload="loadxml('../XML/Question.xml');">
Upper loadxml function run correctly at IE but not at firefox.
alert line display this value ../XML/Question.xml.
but xmlDoc.Load function did not run correctly.
It reply error Access to restricted URI denied
Please anyone help me.
In Firefox the javascript will not let you access files on the user's local file system; there's simply no way to do it. That would be a huge security breach.
This works in Internet Explorer with ActiveX because ActiveX is a plug-and-play application module system (kind of like mini browser plugins) where the apps, like 'Msxml.DOMDocument', have more power than just javascript and can access files on the user's local file system.
But document.implementation is regular javascript, so it has all normal security restrictions, a major one being that the user's file system is off limits.
If the XML file is on the server, you can embed in your html code like this:
<script id="the-xml" type="text/xml">
....your xml document contents here....
</script>
Then you can get the contents in javascript like this:
var sImportXML = document.getElementById('the-xml').text;
But depending on your application, it might make sense to not use the javascript xml at all. Usually, you'd parse the xml on the server side, and communicate with javascript in json or html snippets.

Can someone help me understand AJAX (JSON) problem?

My goal is to create an personal application out of my ActionScript3 video player. I want to be able to hold keep the single .swf file in my browser and through AJAX, pass the .swf the url to my videos. I've chosen to use JSON as my data.
I'm new to JSON and I've hit a wall. It seems completely easy, but at first I wasn't even able to even get my locally hosted .json file into my webapp. It was working when I tried to do this with XML. After a bunch of trouble shooting, it is now in fact getting my XMLHttpRequest.
I'm trying to keep with backwards compatibility as much as possible, and thus I'm using the json2.js library to secure that notion.
My current issue is not being able to parse my XMLHTTPRequest. To be honest, I'm not even sure if what I'm doing is right as everywhere I look for examples, they're almost all pointing to a solution that writes the JSON into the actual webpage.
My external JSON file: test.json.
{ "video":"test.f4v", "thumb":"test.jpg", "title":"The test", "caption":"TEST TEST TEST TEST TEST", "minutes":01, "seconds":43 }
I'm positive the JSON file is valid.
Here is my html/javascript:
<script type="text/javascript" src="js/json2.js"></script>
<script type="text/javascript">
window.onload = initAll();
function initAll(){
var jsonData = {};
var xhr = false;
if(window.XMLHttpRequest){ //Chrome, Firefox, Opera, Safari, IE7+
xhr = new XMLHttpRequest();
} else if(window.ActiveXObject){ //IE5 + IE6
try{
xhr = new ActiveXObject("Msxml2.XMLHTTP");
} catch(e){
try{
xhr = new ActiveXObject("Microsoft.XMLHTTP");
} catch(e) {
alert("Could not make XMLHttpRequest");
}
}
}
if(xhr){
xhr.open("GET", "js/ajax/test.json", true);
xhr.onreadystatechange = function () {
if (xhr.readyState == 4 && xhr.status == 200){
try{
jsonData = JSON.parse(xhr.responseText);
alert(jsonData.title);
document.getElementById("vidtitle").innerHTML = xhr.responseText.title;
document.getElementById("vidcaption").innerHTML = jsonData.caption;
} catch(e){
alert("Unable to parse jsonData.");
}
}
};
xhr.send(null);
}
}
</script>
</head>
<body><div class="vidcontent">
<h2 id="vidtitle"></h2>
<p id="vidcaption"></p>
I'm doing this locally on my server, but I have uploaded the files to my web host and still get the same issues.
Firebug tells me it has the data and I can even read it through the console. Now, The code works in Firefox, but not Chrome or IE8 (IE8 Works occasionally when I put it into compatibility mode, but not always <.< ) I can't test on Safari or Opera right now.
Is there any way I can get this working in these browsers? I have attempted $.parseJSON in the JQuery library, but I was having issues with that as well. I am interested in JQuery as well if anyone can explain the solution with it.
Your JSON is invalid: http://www.jsonlint.com/
Leading 0's are not allowed in numbers apparently.

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