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Js - Create a file and save it to a specific folder in the project

I created an excel file via javascript, but when I need to save it the only option is to have the user open the download window and download the file. I, on the other hand, would like the file to simply be stored in a folder in my project, without the user having the option to download the file.
How can I do this? Thank you

You don't provide enough information but seems that you are doing it on the client side (i.e. a browser), which, in principle, does not have access to the file system on your computer/server.
You should try some Back-end approach, like, in your case with JavaScript: Node.js, or maybe anothers like Python or PHP.

Can a Chrome Extension Dynamically Add JS Files to Local Extension Directory? User Upload or Saved From the Web?

I'm wondering if it's possible to for certain JS files to be added to the web extension directory later?
Like say I have an app where users can select certain settings from within the app and those files (js and html files, images or blobs) are somehow added into the extension from the web. Like some sort of ondemand updater without using any native apps but it seems that upgrades are done by the appstores automatically.
I'm reading the files using ajax and adding them to indexeddb but because it could be more than one file that's getting messy.
Say a user wants a certain feature on the extension and there's an html page, js files and images then this gets downloaded to a certain folder inside the installed extension.
function download() { //only saves to downloads directory
var imgurl = "https://www.google.com.hk/images/srpr/logo11w.png";
console.log('download');
browser.downloads.download({url:imgurl},function(downloadId){
console.log("download begin, the downId is:" + downloadId);
});
}
I also tried the chrome download function above but that only works for the downloads folder not the extension folder.
Is there any way to make a custom updater?! I know we can't save to disk but any leniency or workarounds for the extension folder?! Even something silly like making a shell call to some dos (and linux/mac) thing that saves the file to the extension folder. I can fetch the files, just not save them.

Ok so I'll put it as an answer. This is the solution I'm leaning on which works for my scenario and I've listed some alternatives below:
Having the other files as separate extensions and giving the user an install link instead where they can install that extension, then those child extensions talk to the mother extension and they know the address to the resources in their child extension folder, so the mother gets the just the file locations from the children to load those assets from that folder. The child extensions are like bundles of those html and js with a background script which sends the addresses of these items to the mother.
https://developer.chrome.com/extensions/messaging#external
The drawback is that I'll have to see how that affects the urls like if I inject the html page from the child extension folder into the main interface using ajax then I can't use relative url's to any images in that 'cos the urls are relative to the mother extension folder.. I'll have to rewrite the child extension urls with the absolute paths into the html page to load images and js from the child extension html code which has relative urls.
Pros:
Cleaner and more persistent than indexeddb.
Files can be loaded normally from disk.
Cons:
User has to install separate extensions.
URL structure might be a bit confusing, need to rewrite urls if loading html from child. However this is only for image src's and where the javascript is loaded from so it's not such a big deal.
Other Possible Solutions:
Indexeddb which I'm already doing seems to be the preferred way of doing this but I really do not want to store every html asset in indexeddb. The upside is that while extensions need to be installed, this method can be done silently fetching and adding files without user interaction and indexeddb seems to be somewhat persistent. Might still end up using this because it is silent but having to load each asset from a database sounds like a nightmare.
The File Handle Api might have worked if I was working on Firefox only https://wiki.mozilla.org/WebAPI/FileHandleAPI
I haven't tried the shell copy, maybe if I fetch with ajax and then save to disk using some dos function and then doing different save functions for different OS systems.
Filesystem Api only saves to downloads and doesn't work for extensions anyways, so that's useless.
UPDATE
In windows there isn't any sudo, but this worked without admin priveleges for a subfolder (not on the C:\ root though). It would work for a linux only app very nicely. If I just wanted to save a file to a windows machine this might work.
Shell copy method would be to grab the contents of file with ajax from the local or remote location, output to DOS as a stream to save to file on windows. And do this for every operating system with a shell exec command or detect the OS and do that command. This way I can even put the files in the exact folder location.
Like say I make this sort of command from the contents:
//To append you can use >> instead of >
//folder seems necessary, can't save to root without admin
echo the content I want to save > C:\folder\textfile.txt
I thought of calling it using shell exec that only works in nodejs, so digging through the other answers on
How to execute shell command in Javascript
//full code to save file using javascript on windows
var shell = WScript.CreateObject("WScript.Shell");
shell.Run("echo content to save > C:\folder\textfile.txt");
The shell command doesn't seem to work. i can't find what this is for. There doesn't seem to be a shell command in regular javascript for windows. It seems to require IE ActiveX. Doesn't work with Firefox or Chrome.

Extensions can't modify their sources because the browser verifies them and resets/disables the extension if they change. Also, in Firefox the extensions aren't even unpacked.
The solution is actually quite trivial: save the code in any storage (localStorage, chrome.storage.local, IndexedDB) as a string and then add it in your extension page as a standard DOM script element. You'll have to relax the standard CSP a bit for that.

How to access filename from a folder using JavaScript

I am trying to build a simple website with just an index file and a folder full of icons for our internal purpose. I am making this so that anyone in our team can just access the link and download the icons whenever needed without our help. I am trying to read the icons file name from the folder automatically, so every time we update the folder with new ones we don't have to edit the HTML. I know only JavaScript. Please help me.

An alternative could be to produce a filelist of the files via a script or batch file (depending on OS, something like - in psudeo - ls path/to/images > filelist.txt) which redirect the output to a file that ends up in the same root as the index and images.
This file could then be read via fetch() or XMLHttpRequest() and parsed on client side to provide the basis for the links to the updates files.
This would require an extra step in the pipe-line of course, but could easily be automated using a listener for the image directory that triggers the script, part of your project setup and so forth.

This is not possible. In your case Javascript is running in the browser (client-side). It has no access to the servers filesystem. You need a server-side dynamic web-service (php, node.js, ...)

linking html web page to text editor to practice

I'm trying to link this page http://www.bauer.uh.edu/parks/f1471m.htm to my text editor ( text mate) with a mac.
I even copied the code and pasted it into an HTML file, and made a .js file (the one I'm trying to use to practice with) in the same folder and to use the local tag with no success.
I tried using src="http://www.bauer.uh.edu/parks/f1471m.htm" with no luck.
am I doing something wrong?

I'm making a few assumptions here...
From what you're describing, I think you're trying to directly edit the file. Unless you have write access on that server, what you're doing isn't going to work. Some web development software will allow you to do this, but most text editors don't.
Can you work on the file locally (on your computer's file system) and upload it to the server through FTP?
Many browsers give you the ability to save a page locally these days. That would set up the proper structure for you on your own machine. (FireFox can do this using Save Page)

how to open downloaded excel file when complete download in asp .net

We have a web server, which allows the user to download files (excel), which are dynamically-generated We'd like when a download has completed then it should automatically open client side in the excel.
is there any way to do so by asp.net code or jquery code or javascript code?

Nope. You can't tell the client-side how to handle downloaded files.
Imagine the security issues that would cause.
"you just (accidentally?) downloaded someShiftyFile.pdf.exe, now we MAKE your pc run it!"
Possibilities like that would make virus coders very happy.