I'm working with a .js client and have and object that I need to write out to a file on the server. A couple of questions - file i/o with JavaScript is new to me... I was planning on using jquery and json. I'm using java serverside. I don't have a problem reading what I get back from my servlet, but the file i/o is killing me! A couple of questions:
I can open a file I generated myself via the .js with an $.ajax call, but it's not handling my json syntax (I tried both an $.getJson and $.ajax - handwritten json, so I might (probably) are doing something wrong with it). I used firebug's console and it looks ok...
How can I write my object to a file on the server?
Then, when I want to read it, what do I need to do to process it? Right now I'm using a jsonFilter function (uses JSON.parse if that's available, otherwise eval) to process data that I'm getting from the servlet.
The object I'm writing isn't simple, but it's not super complex either. There's an array that contains an array, but that shouldn't make a difference if the software is both reading/writing it.
Thanks for any help! I'm at a loss - tried alot of different things.
You can open a file located on the server via ajax by querying the file and loading it into a JSON object. You might want to LINT your JSON
You can not write to an object on the server via the client. This is a severe security breach.
Common practice is to change the JSON data and then send it via ajax to server-side code. The server will then do the file IO.
Yes using JSON.parse otherwise eval is indeed correct. I would recommend json2.js
The data should be fine as long as it passes JSONLint.
Your main issue is that it's impossible to write to the server from the client. Get the client to load the data through ajax change it and then query the server to update the file.
js don't have i/o property;
you should use ajax or http request to send message to server,and tell server to do de i/o action...
Related
so I am trying to send JS data, to be more specific, images responses Python file has collected, I need from python to send these images to JS and JS does a thing, (which I'll be coding) and sends the final result back to Python, how possible is that? I have 0 idea of doing that, looking forward for help, :cheers:
You can use API for the process. Post request & get request and so on. Also in Django you can deal with this process. Send variables from views.py and from template you can use them. There is similar question: Django Template Variables and Javascript
I'm want to (or think I need to) use AJAX to accomplish what I intend.
When clicking on a specific link in a list of links, I want to fill the HTML markup below with content of specific subpages. The data is naturally somewhere in the database and actually easily accessible with the CMS's API (I'm using Processwire).
I'm quite new to coding and especially AJAX and all documentation I find online only mention it in combination with a JSON file that would be loaded via AJAX.
However, I don't have a JSON file on the server, that means, according to my understanding, I would need to
store the data I need in a multidimensional php array,
use json_decode to create and then save that JSON-file on the server,
load that file via AJAX and process through more JS.
Let alone keep that JSON-file updated (or create a new one and delete the old one?) since new content will arrive periodically. It seems unnecessarily complicated to me, but what do I know.
There's got to be a better way…
Any help is appreciated.
AJAX is simply a way to make a request to the web server for information.
When you make an AJAX request you ask for a response from a file on a server. So, you can send an AJAX request to a PHP script for-instance.
The PHP script could return anything, JSON is common and very widely used response format, but XML might be another one you've encountered.
So, your request for information is made using AJAX, and the response you get back is JSON.
You don't need to store a JSON file on your server. You just need to make an AJAX request that returns current data in JSON format.
AJAX allows you to do asynchronous HTTP requests.
You can of course ask for a json file, but you can also (for example) call an API.
I suggest you start by reading the the getting started guide for AJAX in MDN:
https://developer.mozilla.org/en-US/docs/Web/Guide/AJAX/Getting_Started
I'm trying to do client-side processing of some data sent in a server's HTTP response.
Here's what I'm working with: I have a web application that sends commands to a backend simulation engine, which then sends back a bunch of data/results in the response body. I want to be able to access this response using JavaScript (note..not making a new response, but simply accessing the data already sent from the server).
Right now, I am able to do this via a kludgy hack of sorts:
var responseText = "{{response}}";
This is using Django's template system, where I have already pre-formatted the template context variable "response" to contain a pre-formatted string representation of a csv file (i.e., proper unicode separators, etc).
This results in a huge string being transmitted to the page. Right now, this supports my immediate goal of making this data available for download as a csv, but it doesn't really support more sophisticated tasks. Also, I'm not sure if it will scale well when my string is, say, 2 MB as opposed to less than 1 KB.
I'd like to have this response data stored more elegantly, perhaps as part of the DOM or maybe in a cache (?) [not familiar with this].
The ideal way to do this is to not load the csv on document load, either as a javascript variable or as part of the DOM. Why would you want to load a 2MB data every time to the user when his intention may not be to download the csv everytime?
I suggest creating a controller/action for downloading the csv and get it on click of the download button.
I am developing a web app which functions in a similar way to a search engine (except it's very specific and on a much smaller scale). When the user gives a query, I parse that query, and depending on what it is, proceed to carry out one of the following:
Grab data from an XML file located on another domain (ie: from www.example.com/rss/) which is essentially an RSS feed
Grab the HTML from an external web page, and proceed to parse it to locate text found in a certain div on that page
All the data is plain text, save for a couple of specific queries which will return images. This data will be displayed without requiring a page refresh/redirect.
I understand that there is the same domain policy which prevents me from using Javascript/Ajax to grab this data. An option is to use PHP to do this, but my main concern is the server load.
So my concerns are:
Are there any workarounds to obtain this data client-side instead of server-side?
If there are none, is the optimum solution in my case to: obtain the data via my server, pass it on to the client for parsing (with Javascript/Ajax) and then proceed to display it in the appropriate form?
If the above is my solution, all my server is doing with PHP is obtaining the data from the external domains. In the worst (best?) case scenario, let's say a thousand or so requests are being executed in a minute, is it efficient for my web server to be handling all those requests?
Once I have a clear idea of the flow of events it's much easier to begin.
Thanks.
I just finish a project to do the same request like your req.
My suggestion is:
use to files, [1] for frontend, make ajax call to sen back url; [2] receive ajax call, and get file content from url, then parse xml/html
in that way, it can avoid your php dead in some situation
for php, please look into [DomDocument] class, for parse xml/html, you also need [DOMXPath]
Please read: http://www.php.net/manual/en/class.domdocument.php
No matter what you do, I suggest you always archive the data in you local server.
So, the process become - search your local first, if not exist, then grab from remote also archive for - 24 hrs.
BTW, for your client-side parse idea, I suggest you do so. jQuery can handle both html and xml, for HTML you just need to filter all the js code before parse it.
So the idea become :
ajax call local service
local php grab xm/html (but no parsing)
archive to local
send filter html/xml to frontend, let jQuery to parse it.
HTML is similar to XML. I would suggest grabbing the page as HTML and traversing through it with an XML reader as XML.
How do I access a property file using javascript. Normally property file is a xml based file.
I java we access a property file like this:
Properties prop = new Properties();
fis = getClass().getResourceAsStream("props.xml");
if (fis != null) {
prop.loadFromXML(fis);
}
String dbUrl = prop.getProperty("dburl");
I want to do the same but using javascript. is there a possible way of doing it?.
JavaScript can't load files, as part of its security model. It can retrieve XML from the server using AJAX, but it can't read files from the client computer.
You can't load any files from the users computer with javascript in the browser.
If the file is from your own server you can load it, like any other ajax, with XMLHttpRequest.
Javascript doesn't use property files, as, either it has all the information it needs in the javascript files or in the html, or it will make an XMLHTTPRequest call to get the information from the server.
The server can look at the property file, and may use information passed in from the request, such as the header information, to know more about the client, to determine what information to pass back.
So, if you want to pass back some localized information, the server would have to get that from the browser request and then it could send back just what is needed for that transaction.
Javascript is different from java, so one limit is that javascript cannot read from the hard drive of the user, and since it is a webpage, the user wouldn't have the property file installed, it would still be on the server.
Javascript can only make requests to the address that that script came from, so there is a second sandbox rule that has to be met.
You may want to better understand javascript, then try to rephrase your question.
HTML5 now allows JavaScript to read local files, via the File API:
http://www.html5rocks.com/en/tutorials/file/dndfiles/