Generate remote XML, and consume from web page, using javascript - javascript

I am looking at a scenario where I want to "consume" an xml/json document and build some visual elements from said date.
Per example, List of bookings for a time period. Lets say data will contain
<unit>
<booked>
<pic>
<booked range>
What I am not sure of, is how to go from accessing a query string, to catching the returned xml. This seems simple, but I cant seem get get my head around accessing the XML returned, from Javascript.
More info:
I am building a mobile app, that will display data, retrieved from XML. (I want to run the url/query string from the app, to generate a custom xml doc, and read XML data returned (not display the web page)
Any advice?

Synopsis
Collect the xml through an ajax call.
Xml response available as dom tree (parsed) or in lexical representation (text)
Have the callback handler process your xml and interact with the dom
options to process your xml:
XPath
Xslt
DOM functions
string manipulation
string parsing ( probably pointless, unless you have special requirements on parsing )
Code
A pure Javscript solution using the XMLHttpRequest ( docs: eg. MDN reference, MDN usage hints; there also exists a tutorial on html5rocks ) might look similar to the following fragment:
var oReq = new XMLHttpRequest();
function eh_onload ( ) {
var xmlhttp = this;
if (xmlhttp.readyState === 4) {
console.log ( "xmlhttp.status = " + xmlhttp.status);
if (xmlhttp.status === 200) {
//
// process your xml here.
//
console.log ( "responseText = '" + xmlhttp.responseText + "'");
console.log ( "xml root element = '" + xmlhttp.responseXML.documentElement.nodeName + "'");
}
else {
console.log('error');
}
}
}
oReq.onload = eh_onload;
oReq.open("get", "http://wsearch.nlm.nih.gov/ws/query?db=digitalCollections&term=cholera", true);
oReq.send();
The code snippet performs an ajax request and registers a callback that will be executed upon completion of the request. As you can see, you may either access the lexical representation of the xml data received or a parsed DOM structure.
Alternative
In case using the jquery library is acceptable to you, you may proceed along the lines of the following code sample:
function eh_xml ( parsedxml, textStatus, jqXHR ) {
// process your xml here.
//
console.log ( "typeof(parsedxml) = '" + typeof(parsedxml)+ "'");
console.log ( "$('term', parsedxml).length = " + $("term", parsedxml).length);
}
$.ajax({
url: "http://wsearch.nlm.nih.gov/ws/query?db=digitalCollections&term=cholera"
, dataType: "xml"
, success: eh_xml
});
The code snippet performs an ajax request and provides a callback that receives the xml in parsed (DOM) representation.
Note & Caveat
The code sample uses a public web service provided by the US NIH returning xml data. This one has been selected randomly and is employed for the sole purpose to have a working PoC. No affiliations exist and the usual legal disclaimers apply.
The code can be tested from the console (eg. in Chrome) opened on the site http://wsearch.nlm.nih.gov/ using the following prelude which loads the jquery library in the context of the site hosting the web service:
var script = document.createElement("script");
script.src = "http://code.jquery.com/jquery-2.1.3.js";
script.type = "text/javascript";
document.getElementsByTagName("head")[0].appendChild(script);

Related

Modify <div> container on click of a button, insert HTML from GET request

Prerequisites
I have a Website, that displays a page with an input and a button. On the other end is a server that exposes a very basic HTTP API. The API is called like this:
http://127.0.0.1/api/arg1/arg2/arg3
where argX are the arguments. It returns raw HTML. This HTML code needs to be inserted into the Website (another domain). There is a
<div id="container5"></div>
on the website. The HTML needs to be inserted into this container. The code returned by the API is specifically made to be inserted into this container, as it uses CSS classes and scripts from the website, i.e.: the code is not valid for it self.
The Goal
Here is what I have: I've got the API to return what I want, and I got a small JavaScript to run on the website to change the contents of the container:
var element = document.getElementById("container5");
element.innerHTML = "New Contents";
This works so far. Now I need a way to get the HTML from the API to the page. By reading numerous SO questions, it quickly became clear that reading HTML from another URL is close to impossible in JavaScript, due to security constraints.
Is there an easy way to do this with JavaScript or do I need rethink the whole process somehow? One last constraint on my side is that I can only insert JS into the website, I can't - for example - upload a new file to the server.
Edit 1: Workaround!
I solved this for me by using a PHP intermediate file on the requesting server:
<?php
echo file_get_contents('http://example.com');
?>
This will generate a site using the HTML content of any URL. Now the requesting site can read this by using JavaScript:
var getHTML = function ( url, callback ) {
// Feature detection
if ( !window.XMLHttpRequest ) return;
// Create new request
var xhr = new XMLHttpRequest();
// Setup callback
xhr.onload = function() {
if ( callback && typeof( callback ) === 'function' ) {
callback( this.responseXML );
}
}
// Get the HTML
xhr.open( 'GET', url );
xhr.responseType = 'document';
xhr.send();
};
This modifies any element:
var element = document.getElementById("resultpage");
getHTML( 'http://localserver.org/test.php', function (response) {
element.innerHTML = response.documentElement.innerHTML;
});
Checkout CORS https://en.wikipedia.org/wiki/Cross-origin_resource_sharing
also JSONP in same article.

Create HTML table from text file using Javascript?

I don't even know if my project is possible. After looking around for a few hours and reading up on other Stack Overflow questions, my hopes are slowly diminishing, but it will not stop me from asking!
My Project: To create a simple HTML table categorizing our Sales Team phone activity for my superior. Currently I need something to pull data values from a file and use those values inside the table.
My Problem: Can Javascript even do this? I know it reads cookies on the client side computer, but can it read a file in the same directory as the webpage? (If the webpage is on the company server?)
My Progress: I will update as I find more information.
Update: Many of you are curious about how the file is stored. It is a static webpage (table.html) on our fileserver. The text file (data.txt) will be in the same directory.
I've recently completed a project where i had almost the exact conditions as yourself (the only difference is that users exclusively use IE).
I ended up using JQuery's $.ajax() function, and pulled the data from an XML file.
This solution does require the use of either Microsoft Access or Excel. I used as early as the 2003 version, but later releases work just fine.
My data is held in a table on Access (on Excel i used a list). Once you've created your table in Access; it's honestly as simple as hitting 'Export', saving as XML and then playing around with your 'ajax()' function (http://api.jquery.com/jQuery.ajax/) to manipulate the data which you want to be output, and then CSS/HTML for the layout of your page.
I'd recommend Access as there's less hastle in getting it to export XML in the right manner, though Excel does it just fine with a little more tinkering.
Here's the steps with ms-access:
Create table in access & export as XML
The XML generated will look like:
<?xml version="1.0" encoding="UTF-8"?>
<dataroot xmlns:od="urn:schemas-microsoft-com:officedata" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="Calls.xsd" generated="2013-08-12T19:35:13">
<Calls>
<CallID>1</CallID>
<Advisor>Jenna</Advisor>
<AHT>125</AHT>
<Wrap>13</Wrap>
<Idle>6</Idle>
</Calls>
<Calls>
<CallID>3</CallID>
<Advisor>Edward</Advisor>
<AHT>90</AHT>
<Wrap>2</Wrap>
<Idle>4</Idle>
</Calls>
<Calls>
<CallID>2</CallID>
<Advisor>Matt</Advisor>
<AHT>246</AHT>
<Wrap>11</Wrap>
<Idle>5</Idle>
</Calls>
Example HTML
<table id="doclib">
<tr><th>Name</th><th>AHT</th><th>Wrap</th><th>Idle</th></tr>
</table>
jQuery:
$(document).ready(function(){
$.ajax({
type: "GET",
url: "Calls.xml",
dataType: "xml",
success: function(xml) {
$(xml).find('Calls').each(function(){
var advisor = $(this).find('Advisor').text(),
aht = $(this).find('AHT').text(),
wrap = $(this).find('Wrap').text(),
idle = $(this).find('Idle').text(),
td = "<td>",
tdc = "</td>";
$('#doclib').append("<tr>" +
td + advisor + tdc + td + aht + tdc + td + wrap + tdc + td + idle + tdc + "</tr>")
});
}
});
});
JavaScript cannot automatically read files due to security reasons.
You have two options:
If you can rely on IE being used, you could use some fancy ActiveX stuff.
Use a backend which either constantly pushs data to the JS client or provides the data on pull requests.
This could work if you had a server like build with Node.js, PHP, ...etc.
JavaScript can read files with the Ajax protocol, but this mean that you need a server.
Otherwise your requests will go through the file:// protocol which doesn't support Ajax.
You can try looking into FileReader:
https://developer.mozilla.org/en-US/docs/Web/API/FileReader
The FileReader object lets web applications asynchronously read the contents of files (or raw data buffers) stored on the user's computer
I've never personally gotten it to work properly, but it's supposed to be able to allow this sort of thing.
Try with XMLHttpRequest or ActiveXObject in IE 5 or IE 6.
Here you can find an explanation:
http://www.w3schools.com/xml/xml_http.asp
Or try this example:
http://www.w3schools.com/ajax/tryit.asp?filename=tryajax_first
It sounds like you just want to get the contents of a static file from your server; is that right? If that's what you need to do, you're in luck. That's very easy.
load('textTable.txt', function(err, text) {
buildTable(text);
});
function load(url, callback) {
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function() {
if (xhr.readyState < 4) return;
if (xhr.status !== 200) {
return callback('HTTP Status ' + xhr.status);
}
if (xhr.readyState === 4) {
callback(null, xhr.responseText);
}
};
xhr.open('GET', url, true);
xhr.send('');
}
If you go with qwest, it'll look something like this:
qwest.get('textTable.txt').success(function(text) {
buildTable(text);
});
With jQuery:
jQuery.get('textTable.txt', function(text) {
buildTable(text);
});

Parsing the Data Returned from a javascript JSON call

This code is on a Button onClick event:
function loadJSONData(url) {
var headID = document.getElementsByTagName("head")[0];
var newScript = document.createElement('script');
newScript.type = 'text/javascript';
newScript.src = url;
headID.appendChild(newScript);
}
loadJSONData('http://api.lemonfree.com/listings?key=2806cdf10605dc9598b1cf3a2387acb7&make=HUMMER&model=H2&zip=80901&distance=100&per_page=25&sortby=Price&sortdir=ASC&year_from=2005&year_to=2008&format=json&callback=processJSONData');
This code is in the Load JavaScript area
function processJSONData(data){
alert( "Id: " + data.response.requestType );
console.log( 'Id:' );
console.log( data.response.requestType );
}
When I press the Button the onclick event fires and the below JSON data is returned.
The problem is that I cannot figure out how to reference the data with it.
I have tried everthing that I can think of to access the data elements.
data.response.requestType,
data.response.result[0].id
response.requestType,
response.result[0].id
etc.
www.jsonlint.com validates the returned data as valid json also
jsonviewer.stack.hu also validates the returned data as valid json.
Any HELP would be greatly appreciated.
Mark
If you enter this into your browser you will receive the data that is returned
http://api.lemonfree.com/listings?key=2806cdf10605dc9598b1cf3a2387acb7&make=HUMMER&model=H2&zip=80901&distance=100&per_page=25&sortby=Price&sortdir=ASC&year_from=2005&year_to=2008&format=json&callback=processJSONData
Your loadJSONData function actually uses JSONP, so you don't need to parse anything at all - data would just be the object.
Only the lemonfree api does not seem to support JSONP, the ressource you linked to is plain JSON - the callback "padding" is missing. And the SOP prevents you from accessing it directly via Ajax, so you'll need to use some kind of proxy.

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.

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

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