I am trying to write my first chrome extension. The workflow goes something like this -When the extension is installed and active if a user hovers over a specific product/ID displayed on the page, the extension retrieves related vendor data about the product with the ID.
This is how I thought about this:
Use jQuery attr to access the ID on mouse over.
Post this ID to a retrieve.php file with .post() method
The retrieve.php file retrieves the data from database
Display the data in a tool tip on the web page.
I have some queries for the above process:
I am able to get this working on a local XAMPP server but how will it work online as the chrome extension will not have access to server. What is the way around to retrieve data without using PHP?
I am able to get the logic working but am unable to place these in respective files - Will all my logic reside in background.js ?
Any suggestions on getting this started will be much appreciated.
You could build a very simple API on your server that responds with JSON to any request it receives after processing it. Like this:
{"firstVar":"foo","secondVar":"bar" }
Your chrome extension can then make an xmlhttp request to this server and and process the returned data.(You could also use JSONP and wrap the response in a callback function which will execute as soon as you have the reponse)
The JS extension will be able to deal with the JSON nicely as it can understand that format so you can then choose to display the data in whatever way you want.
Essentially, what you want is a server that can take an ID posted to it and return the corresponding date in a nice and readable format. And a chrome extension that can make an request to a server and then process the response. Build and test them separately (keep positing an ID to the server and see the response and for your JS side at first instead of making requests to your unfinished API just set a static response to begin with which will be the same as an expected response.
Related
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.
My web application uses file which has been updated by other process. My application reads the content of the file using ajax
xmlhttp.open("GET","/config/myfile",false);
xmlhttp.send();
Once response is received then app parses this response and shows that values on Web UI. The file contains 50 fields and whenever I want to read any single field I need to open whole file.
Is there any way to get the values of single field based on key instead of reading whole file.
As per my understanding we need to read and open file and then parse the response text. But would like to know is there any way to reduce the file calls with any other method.
I want to achieve this to reduce the file I/O operations. Since other processes are writing in to it and at same time my web app accessing to read the latest value.
Any other option would be appreciated.
Note :- I do not have to use any server side scripting lang option.
Regds
I'm a consultant working on a web app that's basically a single page app. All it does is constantly retrieve new json data behind the scenes (like once a minute), and then display it on screen.
Our clients load this app, and leave it running 24/7, for weeks on end. If errors happen when retrieving new json data, the app ignores it and keeps running.
We're rolling out an update, and want the existing clients to either become invalidated, or reload themselves without any user interaction. This feature wasn't "built in" by anyone, and we're trying to do this after the fact.
Is there some way to make the existing clients reload without telling our end users to just reload the page?
The following conditions define the app a bit more:
The app uses jQuery 1.9.0
Runs exclusively in Chrome
Retrieves new json data frequently using jquery
Throws away any errors it finds in json responses and uses old data.
EDIT:
I've had it suggested that we could try the following:
send invalid data through the JSON responses to crash chrome (like 500 megs of data, for example)
send window.location.reload through the JSON response (which supposedly won't work due jquery protecting against this type of thing)
send "script" data in the JSON response and if it gets $.html(....) at some point, then it may run the script as well.
and am open to any suggestions on getting this to reload or kill chrome, so the client is forced to reload the page.
If you're using $.ajax to request your data, and not specifically setting your content type, then you may be able to do the following on the server:
set the content type header to "text/javascript"
respond with javascript, e.g. window.location = "http://www.yoursite.com"
jQuery may eval that, and simply run your javascript.
No it is not possible. As far as I can tell you do not execute code from the JSON response (which is a very good thing). Thus you have no way of altering your current client's behaviour. According to your own statement:
"Throws away any errors it finds in JSON responses and uses old data"
You will not be able to crash the user's browser by sending invalid JSON data as the errors will be suppressed.
You can build in automatic deployment in to future versions by sending an application version number and testing for changes or by using WebSockets (which the application seems better suited to anyway as you can ensure your clients only poll the server when the JSON has actually changed).
If I get it correctly, create a version referance page, and make the client check this page very couple seconds, when you update the file, client will reload itself with this script.
var buildNo = "1.2.0.1";//
var cV = setInterval(checkVersion,(5*1000))//Every 5 sec.
function checkVersion(){
$.ajax({
url:"checkVersion.php?v="+buildNo,
dataType:"JSON",
success:function(d){
if(d.version != buildNo){//if version is different
window.location.reload();
//chrome.runtime.reload(); //for chrome extensions
}
}
})
}
if you cant add extra page, you may just add extra variable to end of your JSON data.
I am trying to make an html app for local use, consisting of an HTML page using Google Maps API V3, a SQLite database, and a SimpleHTTPServer script.
The workflow is the following:
User starts the server and opens the page, which contains a map with a set of markers, and a form with filters similar to those of Google Fusion Tables;
User interacts with form, which sets some parameters for a query;
When the user clicks "Submit", page sends a request to HTTPServer, whose request handler queries the SQLite database and returns the result as JSON/JSONP/something-else;
Some function takes back the data and map is updated;
My doubts are more conceptual than anything else, and specifically I would like to know (how/where to look for):
How should I send a request for the server in javascript, and how to listen back to it?
How should the server send data to the request, in order to update its value instead of refreshing the page?
Sorry if my questions seem obvious, but HTTP is something very new to me, and so is client-server communication.
Thanks for reading!
I think you can use CGIHTTPServer.
ref:
http://pydoc.org/2.5.1/CGIHTTPServer.html
Q:How should I send a request for the server in javascript, and how to listen back to it
A:Please google "ajax". "jquery" is one of the most convenient javascript library for ajax.
Q:How should the server send data to the request
A:just use "print" in python script which is called by CGIHTTPServer.
In this case, the output of "print" will be the response to http client(web browser).
In the script mentioned above, you should extract request parameter sent by http client,
with "do_Get()" or do_Post() function.
Lets say there is a url out there e.g. www.website.com/data.jsp
the link has the following JSON data
{"successful":"true","rows":[{"zip":"65472","user_id":"10843","name":"Rufio"}]}
I just want to be able to extract this data at runtime however I am having a hard time getting it using getJSON
$.getJSON("test2.jsp",function(result){
$("div").append(result.rows[0].user_id + " ");
});
Now if I run it using a local file with the data residing in test2.jsp as shown above it appends the user_id. However when I try to access "www.website.com/data.jsp" instead nothing happens. I don't believe the website is configured to work with JSONP either.
I need a way to figure out how to pull this data from the website at run time. Does anyone have any solutions or workarounds?
p.s. Is this something that might need to be sorted out on the other end? The people who own the website set this scenario up to be like a fake api call like typically you would pass in parameters to get back the specific information that you would need. In the case of this endpoint or url it just returns a single record or the file just contains the data listed above. They would like me to extract the data from their url at runtime.
You can't make a normal ajax call to to this other domain due to same origin policy.
You can use JSONP to load the remote page, but looking at that example output you wouldn't be able to access the data unless the remote site is setup for JSONP (assigning the JSON to a variable, calling a callback function, etc).
You could create a server-side passthrough script of your own. You don't mention what server-side technology you have available, but if you can use PHP, you do a passthrough like this:
<?php
echo file_get_contents("http://www.website.com/data.jsp");
?>
PHP (or any other server-side language) can fetch the remote data, and now you can use ajax to call your own script (which works since you're on the same domain).