Basically, I am encoding a wav file using libopus.js on the client side, now on the server side(node.js) I have to decode it using the same library, this is where I am getting lost, not sure how adapt the libopus.js for the server, to make things easier, it is present in minified form.
so what are the steps I have to follow to port a client side library to node.js.
I can't comment due to low reputation, the usual porting to node js usually means exposing the variable via exports instead of on the window, for example for the Opus which is defined in https://github.com/kazuki/opus.js-sample/blob/master/opus.js
you'd do exports.opus = Opus; and then in node you'd have:
var opus = require('./libopus').Opus and you will have that object.
However, from a fast glance it seems that it works with buffers etc which I am not sure how they port from browser to node js but give it a try I guess.
Related
I have some pure JS code and HTML and CSS on my localhost:8000 server. I have installed node.js and I am able to use it without problem testing it on the VS code terminal. However, I want to integrate the file reading mechanic of node.js into the code that I am running on the localhost:8000 server. I want to put this node.js code into my webpage on localhost:8000
const {readFileSync, promises: fsPromises} = require('fs');
function syncReadFile(filename) {
const contents = readFileSync(filename, 'utf-8');
const arr = contents.split(/\r?\n/);
console.log(arr); // 👉️ ['One', 'Two', 'Three', 'Four']
return arr;
}
syncReadFile('./locations.txt');
I have tried copy and pasting it into the js file for the webpage, however when I run it, the console says
Uncaught ReferenceError: require is not defined
at window.onload (index.js:23:46)
index.js:23:46 is the line where const {readFileSync, promises: fsPromises} = require('fs'); is.
How do I fix this?
I think you need a better understanding of how NodeJS works:
Node.js® is a JavaScript runtime built on Chrome's V8 JavaScript engine.
A JavaScript runtime is (in this context) a program that runs in a machine, with tools to interact with that machine. In development, the context of that machine is the context of a Server.
Now, JavaScript found it's use in the HTML script tag, that's the most "vanilla" way to execute JS in it's home, what it's most used for. In this context, JavaScript is running as a Client.
What makes NodeJS, different from executing the same code in an HTML file you can already execute without installing NodeJS?
It's as vanilla as you can get after you "force" JavaScript to be executed in the Backend, but for it to be used as a webserver, there are some tools that need to be ported, converted or even created, some of these tools, like the File System (fs) are specific to NodeJS.
That's it! TLDR is that your code won't work because it's being executed in the wrong place. You can fix that in many ways, like this one, but maybe you can find a better path understanding how NodeJS works
Browsers cannot access file systems like that. Nodefs will not work within the browser
The NodeJS modules only works on the server side, you can't use it client side (that also include the require() syntax).
If you want to read a file from the server, you might want to use an AJAX directed to the route that has a controller to read the targeted file, which then the result of the AJAX is handled client side with vanilla JS.
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.
I have a website(client) with a bunch of buttons, the site sends the value of those controls to a .js file(sever) through a websocket. Both are connected through the same port I'm using node.js and ws.
How do I call a C function from the .js file in order to perform server side calculations? Is that even possible?
The key word here is “Foreign Function Interface”, or FFI for short. It turns out that there's a package on NPM called ffi that would probably do what you want.
V8 (which node.js uses) has functionality that may help.
https://code.google.com/p/v8-juice/wiki/BindingFunctions
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.
I want to write a function in javascript which creates a file and write some content to it, iam working with firefox, can anybody help me in this case.
Thanks...
You can write files in JavaScript in Firefox, but you have to use an XPCOM object (internal browser API). This is not allowed for JavaScript loaded from a web page, and it is intended to be used by JavaScript running inside a Firefox add-on (with high level of privileges).
There is a way for unprivileged (web page) JavaScript to request more privileges and if the user grants it (there will be a pop up dialog asking for permission), the web page code would be able to write to a file.
But before you read further, a warning:
This is not standard JavaScript and I would not recommend this approach unless you are developing a very specific application, that will be used in a very specific way (like for example, http://www.tiddlywiki.com/ a client-side JavaScript-HTML only wiki).
Requesting XPCOM privileges on a website is a bad practice! It's basicly equivalent to running an .exe you just downloaded from a site. You are asking a user to grant full access to their computer (read, write, execute) with the identity of the user running Firefox.
Request permission to use XPCOM (this will prompt the user for confirmation, no way to avoid it):
netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");
Then, write to a file using an XPCOM object (example code from Mozilla Developer Network):
1. // file is nsIFile, data is a string
2. var foStream = Components.classes["#mozilla.org/network/file-output-stream;1"].
3. createInstance(Components.interfaces.nsIFileOutputStream);
4.
5. // use 0x02 | 0x10 to open file for appending.
6. foStream.init(file, 0x02 | 0x08 | 0x20, 0666, 0);
7. // write, create, truncate
8. // In a c file operation, we have no need to set file mode with or operation,
9. // directly using "r" or "w" usually.
10.
11. // if you are sure there will never ever be any non-ascii text in data you can
12. // also call foStream.writeData directly
13. var converter = Components.classes["#mozilla.org/intl/converter-output-stream;1"].
14. createInstance(Components.interfaces.nsIConverterOutputStream);
15. converter.init(foStream, "UTF-8", 0, 0);
16. converter.writeString(data);
17. converter.close(); // this closes foStream
You can find more information about I/O in Firefox using XPCOM here: https://developer.mozilla.org/en-US/docs/Code_snippets/File_I_O
Javascript from websites cannot access the local file system.
If you like to store data either store it on the server or in a cookie.
writing to the file system directly from a browser is prohibited for security reasons. With html5 however it'll be possible to have offline storage support. Take a look here.
Grz, Kris.
Javascript executes in a client-side context.
http://www.tek-tips.com/viewthread.cfm?qid=1171273&page=1
There will be an API for this.. File Writer API. The early specification is here:
http://www.w3.org/TR/file-writer-api/
It is not implemented in any browser yet.
Update: It seems there already exists an implementation. Check out http://caniuse.com/filesystem and http://www.html5rocks.com/en/tutorials/file/filesystem/
While everyone who's responded that javascript does not have the ability to write files on a remote server are correct, and this is true for security reasons, what you want to accomplish may still be possible.
For example, if you wanted to make it possible to create a file on your website with the use of javascript, you can do so with some server side scripting language and and AJAX call.
Example:
You have a file on your server called update_last_access.php which will create a file which stores the last time the file was accessed in some arbitrary file.
If you then had your javascript function make an AJAX call out to that script, for instance, in jquery
$.get("update_last_access.php")
Then this would execute the server side script and write to the file.
Before any more help can be provided for you, you're going to have to clarify what you're trying to do.
You can read files from the filesystem in JavaScript with Firefox 3.6 - see my EPUB reader proof of concept, for example.
You can't write files directly from JavaScript, though. You have to go via a server.
Mozilla is planning to include FileSaver to Gecko 9:
https://bugzilla.mozilla.org/show_bug.cgi?id=557540