I performed a number of searches but the search terms are very common and I was not able to find an answer to my question.
What are the disadvantages of testing ones Javascript by simply opening a local file in the browser over running a local server using, e.g DAMP, MAMP or WAMP?
Generally speaking, it makes no difference where a Javascript file is served from. The Javascript code will be executed in exactly the same way, since the Javascript interpreter lives on the client-side.
The only difference would be when you are making ajax requests from your Javascript. Some browsers (chrome, firefox) prevent ajax calls to local files, even when the request is coming from a local file, though this can be disabled. When using a local server however, this would not be an issue, as the requests are treated like normal HTTP requests.
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I'd like to find an easy way of reading and writing files (stored locally) from my program running on a localhost server. If I use const fs = require(fs) it can't find the Node module from the server. This makes sense. Is there any way of accessing that file from my javascript easily, with similar functionality to the fs module?
It appears that you aren't quite understanding how the client/server architecture works for an http server and the browser.
There's an http server that runs in nodejs. That has access to the local file system using the fs module. This is server-side code that runs in the nodejs execution environment.
There's an http client (the browser). It makes an http request to your server, the server sends back an http response and the browser gets that response and processes it. If the request is for an html page, then the browser gets that HTML, parses it, displays it and then runs any scripts embedded in the HTML page. The scripts running in the HTML page are running in the client/browser (not on the server).
Javascript running in the browser does not have access to nodejs modules like the fs module. It only has access to the libraries that the browser makes available. Absent special browser add-ons (with elevated privileges and associated security risks), scripts running in the browser in HTML pages do NOT have access to the local file system. This is for security reasons as you don't want random web pages that just happen to click on to have access to anything on your local hard drive.
So, you generally do not access local files from your browser Javascript. Instead, you either store data in LocalStorage and fetch the data from that or you store the data on the server (on behalf of the specific user) and that data is either included in the web page (so the Javascript running in the web page can use it) or the data can be requested from the server by the browser Javascript (using Ajax calls).
I want to execute a nodejs script from a html file.
I'm trying browserify but i'm getting many errors like "http.createServer is not a function".
Is there any alternatives to browserify?
No alternative to browserify is going to let you do things which are simply impossible in a browser environment … including starting an HTTP server.
You cannot execute node.js scripts on the client side.
Actually, that statement isn't entirely true. If a script contains only code that both the browser and node.js can run, or can somehow detect which environment it's running in and switch over to code friendly to that environment, then it will work. But a script is limited to the capabilities of the environment it's running in, so calls like http.createServer() will not function in the browser. It's not defined in the browser, and probably never will be. That's too dangerous from a security perspective.
What you can do is create a server-side API in node.js, and have the browser call it through AJAX. The script serving up your API will be running in node.js, so it can do anything that node.js can do. However, because that code isn't running in the browser, it won't be able to affect the browser, except by whatever it returns.
I suspect that you actually need two scripts -one on the server and one on the client- that communicate with each other. How you set up that communication is up to you, but if you're going to be starting servers in response to AJAX calls, then you're going to need to be very careful about security. Still, this is doable; apps like webmin are common.
Starting a server on browser won't be possible.
No sane browser would allow that as it can lead to drastic security loophole and attacks.
I taught myself programming so my knowledge is very fragmented and now I have encountered a fragment I know nothing about. Sending and receiving Date. In addition I want to do it across domains. I know about the security policies that prohibit this but have read about some solutions. I still can't make sense of it in relation to my challenge.
What I want to do:
I want to build a plugin that sends data to my server when a function is called. The function is bound to an event listener.
this plugin contains of a little html-form and some js in the back. i want to send json or simular.
my questions:
I) how do I send data to an other server?
II) how do I receive this data? I know about parsing and dom but all I did so far is handle requested data. now this data is posted to my server-app without me knowing beforehand. the data is used to update a DB. the backend is coded in JS or python. I would prefer JS for compatability reasons.
III) how can I test the cross server connection on my local machine? especially without an active internet-connection?
I don't expect a complete guide or the code i need. just the resources and where to get the knowledge-chunks I need to build this.
Thanks a bunch in advance!
I) how do i send data to an other server?
You may use AJAX (or jQuery.ajax a more convenient way)
II) how do i receive this data? i know about parsing and dom but all i
did so far is handel requested data. now this data is posted to my
server-app without me knowing beforehand. the data is used to update a
DB. the backend is coded in JS or python. i would prefer JS for
compatability reasons.
As long as you send some data via AJAX, the browser makes a HTTP call and you could receive the data from server-side. Both JS or python would compatible with your client-side javascript and seldom do there have compatibility issue.
III) how can i test the cross server connection on my local maschine?
especially without an active internet-connection?
localhost and 127.0.0.1 is treated as different host and I usually use these to test cross server scenario. One issue of AJAX is that browser usually disallow Cross Domain calls unless you specify Access-Control-Allow-Origin headers.
While I was developing some web apps, to me it became optimal to use a web service to interact with the server, and the rest I was enjoying to do with client side (JQuery). but when I was testing my code, I encountered a huuge hole in it, and i don't know how to prevent it.
The problem is that I can easily inject javascript and run any functions including webmethods from firefox's firebug tool.Is it a something known, and what should be done to prevent it.
THank you
This is not a hole at all. The client can only run JavaScript code on the page that they have downloaded from you on their own computer. It has no affect on your site at all.
As for the ability for them to make requests via JavaScript -- well, they can make requests via the browser too. What's the difference? Just make sure that your server properly validates all requests -- it should treat any request as if it were as malicious as possible.
I am working on a file upload system which will store individual parts of large files on more than one server. So the distribution of a 1GB file will look something like this:
Server 1: 0-128MB
Server 2: 128MB-256MB
Server 2: 256MB-384MB
... etc
The intention of this is to allow for redundancy (each part will exist on more than one server), security (no one server has access to the entire file), and cost (bandwidth expenses are distributed).
I am curious if anyone has an opinion on how I might be able to "trick" web browsers into downloading the various parts all in one link.
What I had in mind was something like:
Browser is linked to Server 1, which provides a content-size of the full file
Once 128MB is served, Server 1 will intentionally close the connection
Hopefully, the browser will try to restart the download, requesting Server 1
Server 1 provides a 3XX redirect to Server 2
Browser continues downloading from Server 2
I don't know for certain that my example works, as I haven't tested it yet. I was curious if there were other solutions someone might have?
I'd like to make the whole process as easy as possible (ideally requiring no work beyond a simple download). I don't want the users to have to use another program (ie: cat'ing the files together). I'd also like to not use a proxy server, since it would incur extra bandwidth costs.
As far as I'm aware, there is no javascript solution for writing a file, if there was one, that would be great.
AFAIK this is not possible by using the HTTP protocol. You can probably use a custom browser extension but it would depend on the browser. Another alternative is to create a Java applet that would download the file from different servers. The applet can accept the URLs to the different servers as parameters.
To save the generated file:
https://stackoverflow.com/a/4551467/329062
That solution stores the file in memory though, so it won't work with very large files.
You can download the partial files into a JS variable using JSONP. That will also let you get around the same-origin policy.
Javascripts security model will only allow you to access data from the same origin where the Javascript came from - i.e. not multiple servers.
If you are going to have the file bits on multiple servers, you will need the user to load the web page, fetch the bit and then finally stick the bits together in the correct order. If you can manage to get all your users to do this (correctly), you are a better man than I.
It's possible to do in modern browsers over standard HTTP.
You can use XHR2 with CORS to download file chunks as ArrayBuffers and then merge them using Blob constructor and use createObjectURL to send merged file to the user.
However, I suspect that browsers will store these objects in RAM, so it's probably a bad idea to use it for large files.