i have a c++ file which reads values from a sensor and I want to display those values on a website dynamically. So Im looking for a way to pass these values(integers) from my cpp file to an javascript which displays them on the site.
My first, simple try was to write the values into a js file as variables every second from my cpp script. The Js then uses this file as a source and displays its variables on the site:
cpp:
fprintf(file, "var mx=%d, my=%d, mz=%d, ax=%d, ay=%d, az=%d, gx=%d, gy=%d, gz=%d;\n",
imu.raw_m[0], imu.raw_m[1], imu.raw_m[2], // M = Magnetometer
imu.raw_a[0], imu.raw_a[1], imu.raw_a[2], // A = Accelerometer
imu.raw_g[0], imu.raw_g[1], imu.raw_g[2] // G = Gyroscope
);
html/js:
<script src="./imu.js" type="text/javascript"></script>
The Problem now is of course, that I need to refresh the page all the time, because the imu.js file is cached by the website.
I'd rather have a way to directly pass to integers from the cpp file to the js script. I read something about json or Googles V8 script. But I'd like to hear your suggestions first.
By the way, Im running this on a raspi, if this is important.
Thanks for your help
EDIT:
I'm goning to try it with a mysql database, in which my cpp file writes the data from the sensor with Connector/c++ from http://dev.mysql.com/doc/connector-cpp/en/ and my website reads them.
You could compile your C++ code into a Node.js plugin, you can then register a JavaScript function with your plugin which the C++ calls when it updates the value. That way you can pass values directly from C++ into Javascript in a managed and controlled way.
Node.js has the added benefit of being able to host your webpage and do all the Websocket and HTTP stuff that can be a pain in C++.
You do not have to refresh if your script is smart about how to access the data file! In case you do have a webserver at hand: Take care that your data file is accessible by your webserver and then let your script request the file via ajax (link to w3schools)
I'm doing something similar on a BeagleBone Black. With websocketd you can turn pretty much any program into a websocket endpoint and then send data via stdin and stdout commands. This would be a particularly good solution for you since websockets are designed to handle information that's constantly changing.
Related
I'm a total novice in web development. I'm interested in using D3 to create interactive visualizations for my (insurance) work, not for sharing on web. The visualization would need to be pretty self-contained so non-tech-savvy business users can view it without special software setup--just the usual browser, internet access, and access to the same LAN locations I have. Below is my initial investigation into viability.
1) I can save this HTML example to my local machine and view the chart in a browser, no probs: https://bl.ocks.org/mbostock/b5935342c6d21928111928401e2c8608
2) Then I tried a visualization that uses a data file.
https://bl.ocks.org/mbostock/2838bf53e0e65f369f476afd653663a2
I went to the data source website and downloaded the .csv. Simply changing the file address in the d3.csv() command to my local drive didn't work (as I mentioned I'm a novice)
Can anyone show me how to make (2) work locally? I found some related answers
Loading local data for visualization using D3.js
Reading in a local csv file in javascript?
but still over my head--if someone can work the example (2) above I can probably understand better...
There are two techniques you can use to load d3 data without a server:
load the data yourself without using d3.csv() helpers.
use data-urls with d3.csv() to avoid server loading.
Loading the data yourself without d3.csv()
Your first example: Stacked Negative Values works because data is defined at the top of the page without using d3.csv():
var data = [...];
...
// d3 operates on the data
Your second example: Nested TreeMap doesn't work because the data is loaded by d3.csv() which takes a path, which ordinarily takes assumes a server:
d3.csv("Home_Office_Air_Travel_Data_2011.csv", type, function(error, data) {
...
// work on data within the anon function passed to d3.csv.
Using data-urls with d3.csv()
However, if you use a data-url as the path, you can get this to work without a server:
var data = [...];
var dataUri = "data:text/plain;base64," + btoa(JSON.stringify(data));
d3.csv(dataUri, function(data){
// d3 code here
});
Adapted from: Create data uri's on the fly?
As an aside, you may be interested in a Middleman plugin I wrote that creates self-contained d3 HTML pages that can be run from the file system without a server using these approaches:
https://github.com/coldnebo/middleman-static-d3
Most modern browsers (chrome, mozilla) have full built in html5, css3, and javascript support without need of a webserver (this is the preferred route for developement).
For example, if you're using chrome all you need to do is set the allow local file access flag: How to launch html using Chrome at "--allow-file-access-from-files" mode?
In mozilla set the about:config key security.fileuri.strict_origin_policy to false.
Again, these are options for loading local files without a webserver, but setting up a webserver is a relatively simple task that is the most recommended route.
you'll need to run a local server like python's SimpleHTTPServer to get this to work locally. once you've got it installed, it's as simple as running a single command in your terminal.
however, since you said that your end users should be able to access it through the browser, do you mean that you'll host it online? if so, they'll be able to view it correctly on the server
Notice how in the first example the data in hard coded into the html page with the variable name data? The data is already here so you won't need a server to go and fetch the data. On the other hand, in second example the data is not hardcoded and is fetched with a server. If you want this to work like the first example you will have to hard code the data into the web page.
You may want to use SERVED by Ian Johnson, its pretty good.
http://enjalot.github.io/served/
I need to have the functionality in the server side in order to hide the implementetion to the final user.
I didn't find a topic with this kind of solution.
I have a .js file with functions I use within the html5 file.
The js files are "called" in the html by using the script tag, but through the url the user can track them and see the .js file content. I don't want this to happen.
$getScript() does the job, but again the url can be cathched, thus the file content too. Much the same with $ajax function.
Everything work ok, but I want to hide the js content.
The .js file is something like this:
var x, x,....
function A(){...}
function B(){...}
and so on, I use A(), B() functions in the html.
Which is the best approach to get the content file from the server without doing the url visible?
Server: nodejs. (I send some json files through socket.io correctly, but I don't know how to achieve this other issue.
Thanks in advance, best!
If you are sending sensitive information to the client then you are doing it wrong. No matter if the client has the URL to the script, they will still be able to find it if they are determined as long as it is sent to their computer.
Find a different way to accomplish what you are trying to do without sending sensitive information to the client. It is not safe.
Inside HTTP adapter, I am getting JSON object back from REST service. I need to do some parsing of the reply before returning it back to the client.
I figured I can have another JavaScript file to do the parsing, so not to clatter my adapter.js too much.
What I don't know is how to make the 2nd java script file available in my adapter JS.
On client side I would use something like $.getScript("some.js");
JAVA classes can be accessed simply with classpath.className, but I can't find any references on how to load another Java Script file!
Please, help!
You cannot have additional JavaScript files referenced from adapter's JS.
I have php made website. It runs on windows machine. I have a javascript that i have tested that gets me the adobe version used by clients. The problem is that by running the code I'm able to retrieve the Adobe Reader version but cannot saved the output to a file on my server end.
Here is the Javascript code. I took this code from sister stackexchange website.
http://jsfiddle.net/EGbY5/3/
What is the best way to save this information from js? Should i use js or any other scripting? I read this from google that you cannot use js to save files on server? If this is true is there any other way.
I would suggest using AJAX (or a form, if you want the user to explicitly know this is happening) to send a request to your server side code detailing the information you have collected with the script.
The advantage of AJAX is that you can do all of this without the user being explicitly aware of it. The disadvantage is that you rely on their browser supporting Javascript, but since you are already collecting information using Javascript this problem is mute.
Ajax'll do it.
JavaScript source:
var adobeVersion = CheckAdobeVersion();
$.post("script.php", {version: adobeVersion}, function(){});
PHP source:
<?php
$version = $_POST['version'];
write all text to a file("my file.txt") // Pseudo code...
?>
again. I'm making a PL/SQL generated HTML5 web page. It's running a Oracle 10g XE server. Okay, now when the setup is clear, my problem - I need to include a Java Script file in the page. Simply
HTP.P('<script type="text/javascript" src="js/ScriptFileName.js"></script>');
Doesn't work of course. So i created a folder object and granted read,write to PUBLIC. Then changed the string to match the newly created object, instead of path. Still doesn't work. I know, i can write
HTP.P(<script type="text/javascript"> MY JAVA SCRIPT HERE</script>);
And i've done so with other scripts(Even had to write CSS this way). But this time this will not work. Reason being - the JavaScript i'm trying to run was normalized(or rather unnormalized), so it's written all in one line. And there is a lot of it too. I tried to reverse it to normal, but faild many a time.
So, I went online and searched for a solution. Found one. It seem's that this include should go not to the page, but to server config. Makes sense, since PL/SQL is server sided. But when i went looking for the usual httpd.conf, it's nowhere to be found in Database directory.So i went online again, result - NOT A WORD OF WHERE THE HELL ARE HTTP SERVER CONFIGS IN 10gXE IN ANY ORACLE MANUALS. Searched some forums - exactly 1 person asked where httpd.conf in XE is, and didn't get an answer. Please, help. I'm desperate.
P.S. I don't use APEX. I don't get that mumbo-jumbo. So i write in Notepad and run the scripts in SQL line.
Firstly, XE has its own built in HTTP server called the 'Embedded PL/SQL Gateway' or EPG. But you don't HAVE to use that. You can use an Oracle HTTP Server with the mod_plsql plugin. Or you can use the Apex listener.
The question is on what server is "ScriptFileName.js" ?
Is it a flat file on the database server ? If so, you'll need to use the Oracle HTTP Server (or Apache or similar) to serve it. The database is pretty much unaware of files on its server and the EPG can't deliver them. [At least not in any practical sense, you could do weird things with chicken entrails and UTL_FILE, but you don't want to go there.]
Is it a file stored in the database ? That sounds exotic, but it is pretty much how all the CSS, images etc are served up through the EPG. The best explanation on how to get files in and out of there is by Dietmar
Is it a file stored on a separate machine ? Often the best answer. The "src=" directive will be read by the end users browser. That will do an HTTP get to the URL. It doesn't have to be a URL on the same domain/host as the rest of the page.