javascript php execute database script(AJAX) on page leaving - javascript

I've got the following issue:
I'd like to execute an AJAX request through JS, which would call the mysql query and clear some data in database(UPDATE and stuff,whatever) when user is leaving my web page.
Does anyone have any ideas how to do such thing?
I mean I'm only missing one piece of the whole process: JavaScript function(event or something).

Related

How to display an animated icon during python function processing in django?

I am trying to develop an application with Django. I have a form in my HTML file which will pass same data to the server. At server side, my python function(called submit) will receive the posted values and process them and then redirect the user to a new page.
Question: How can I show a loading gif to the user until my python function is processing posted data and finished? I searched on the stackoverflow about this question and there are some answers (this and this and this) but the answers are for finishing Ajax functions, or there is no explanation how can I identify when my python function has been finished or is for flask framework.
Any help would be greatly appreciated.
This is rather simple. First you will have to download font-awesome.css from here http://fontawesome.io/.
Then create one element like <span class="fa fa-spinner"></span> this element will be hidden by default. Set it visible at the beginning of your ajax call and hide it once you have receive the response.
If you want to show your own image, the logic should be the same.

Using JavaScript to send String to Servlet, and Results from servlet back to JavaScript

First of all: sorry for my bad grammer. English isn't my native language, but i will try to exlpain my problem as simple as i can.
I'm working on a web-application, where user can enter a link. (Question 1) This link should be send to the server/servlet and will be progressed to other things. (Question 2) After the progression, the servlet will send a json-array (?) back to the javascript-part of my app.
I'm completly new to this kind of stuff, but its very important to me, to find out how this works or better, how i can make this work. Its actually very simple, but i used plenty of weeks and cant figure it out.
The application is using the SAP UI5-libs (Question 3), where i would also like to know, if there is any possible way, to parse JSON with the UI5 libs.
I hope, i could explain my problem good enough, so i can get some help. Thanks to all!
The 'sending' of the string to the server/servlet would happen via ajax in either POST or GET form. That is up to you.
I recommend you use a javascript plugin like jQuery (JQuery Ajax API) because the regular ajax code is a bit messy.
As for the servlet/server communicating back to the client is as simple as writing to the page. In a typical servlet context it would be something like
out.print("This is a message");
where Ajax automatically returns the content of the entire page upon callback.
So in conclusion:
Consider test.jsp your servlet. I wish to send "Hi" from the client (being the browser) via GET to the servlet and I want the servlet to say "Hello" back.
I would open an ajax request of type GET to the url "test.jsp?param=Hi". In the servlet I receive this page request and process it. The servlet discards the parameter because it is not used and outputs "Hello" to the page.
In the client the ajax will have returned "Hello" and I can use this to put it into a var or whatever and all of this happened while not refreshing and not navigating in the original document where I did the javascript.
Another way is using websockets where you basically use sockets in javascript to send and receive any kind of data.
Also please check out this possible duplicate question: How to send a string to a servlet from javascript using xmlhttprequest

How to pass javascript variables to rails variables

How can I pass a javaScript variable into ruby. I want to do something like this but I don't know how to express it.
function save(){
var g = document.getElementById("self").value;
<% #owner.info = g %>
}
Another possible work around is that i would need to be able to extract contents of a text area through rails and not javascript.
Can anyone help me?
What you are attempting to do doesn't make sense with a vanilla rails installation and javascript. Here's a good workflow that accomplishes what you're trying to do along with some details:
1. A page is requested from the server
The ruby code that runs rails and your application is executed on the server. The server receives a request, executes the ruby code, and sends the response as an html document.
2. A user gets the response from the server
The user's browser receives the html and turns it into a pretty web page. It's at this point that any javascript related to your application is executed in the user's browser. The connection with the server has been severed and no further ruby code will be executed until another request is made.
3. The user fills out an ajax form
On the page rendered in step 2, you have a form. Following this guide you can tell this form to submit via ajax. That means instead of requesting a new web page, the browser will send a special request using javascript to the server. The server can save the form values to your database and send a response back to the browser. All the while the user hasn't left the page they are currently viewing.
Alternatively you can skip the ajax and have the user submit the form, but you'll need to redirect them back to the page they were viewing (and probably adding a note the form they submitted was saved).

HTML5 executing query without postback

I am using html5, javascript and JSP for my project. I want to know if there is some method that i can used to execute a query from my servlet without actually posting back the page. i know it can be done in ASP.net but i do n't how it can be be done in java script and JSP. Actually i have a dynamic webpage displaying data from server.what i want is that in a click event of button i want to execute a query form server and update it on the page. i know i can submit the form but it will submit the page which i want to avoid.Any suggestion......
regards
nquazi
You can use an AJAX request to submit inputs and get back an output without reloading that page. Here is a previous stackoverflow answer that shows you how to do a HTTP GET request.
HTTP GET request in JavaScript?
You will then need to process your inputs, run the query, and send back an output on the backend server.

Is there any way to call JavaScript function from a perl script?

I am trying to write a Perl script that will take a user parameter from command line and with his parameter, Perl script will call a JavaScript function in a HTML page. How can I go ahead to with this?
Not that I've seen. Perl is strictly server side, and JS functions you're talking about are on the client.
The closest you would get is have the Perl script write a block into the HTML page so that the page fires it on load to perform the action. But that's a little shaky at best to do.
It depends on whether the browser or server will be taking the first step.
If the server needs to run code first and then execute some JS, then #skyburner's solution would work. Essentially you would already have some functions defined on the page, but then you would dynamically add a block of JS to call whichever function you need to.
However, if the Perl is being run due to a user's action on the current page (such as clicking something or submitting a form), then AJAX would be the way to go. You would use JS to submit an HTTP request to the Perl script. The Perl would then return some value back to the JavaScript and execute some function based on this result. This would all happen "behind-the-scenes" without the user leaving the page.
If I understand correctly about what you want, since not all the browsers support socket, this is what you can do:
Have an ajax service call periodically sending requests to the server for update
Once the the parameters from the command line are taken, you can send the result along with an ajax response back to the page, and call the function in the ajax request callback function.
Also, another option, you can use reverse ajax to accomplish this. See Wikipedia about reverse ajax (comet), especially Ajax with long polling.

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