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Would like to write a javascript that helps me to find documents in a folder

I would like to write a js for an offline website (located on a local Windows server or any other server). It's supposed to look for files like PDFs in several directories and display them as search result on the "website", which isn't a real website, since it's on a local server and not in the web. The PDF is supposed to open in the browser after clicking it. I already have this kind of search engine as a php file, which I wrote with some help from friends. I also want to share this site with other friends. Basically I'll send them the whole folder with the html - document (or the .php site), so they can use it to search for certain pdfs in the folder. Its like a offline wiki for medical research documents. But I don't want them to always install php on their local servers, so they can run my php-searchmachine, thus I need to write it new as a javascript. By google and stack overflow I came across this solution https://www.codegrepper.com/code-examples/javascript/find+file+in+directory+javascript but it seems like that this needs node.js, so all have to install node.js, which is similar to installing php, I guess (im not familiar with node.js). Also I'm not sure if node.js is running on a normal client or server, which is not a webserver.
How can I start with such a project? Is javascript the correct attempt to solve this?

Windows Search has the ability to search PDF contents when boosted by a PDF (index) iFilter, this means the user can search and find instantly a new search word or a saved search it took only a second to hand enter this search (actually took longer to save for double click next time) just for illustration I chose a word I knew was in one file and actually found it is also in two other PDFs.
The problem for your JS coding is how to use JavaScript to interface with Windows Search since using explorer I could not run that search on a remote server shared library drive (I could see their contents as per second screen but for search, had to pull a local library copy down to my documents) and that is where your JS skills come into play. Personally I would avoid JS and use a VLC method to share view via a remote Lan server or simpler invoke a plain text indexed local copy of remote files for download as and when required.

Printing using Nodejs

I am having a really hard time figuring out how I am going to handle printing in my Nodejs application. I have a website where there is a bunch of purchase numbers. I want the users to print this numbers in a click of a button. These numbers are dynamically generated after querying the database.
I started using this npm library to print the purchase number. When I am developing in my local computer this library is working fine. I made it so that each time the user presses a button in the front end, I make a post request to my Nodejs Server which prints to the printer that I configured locally.
The problem is that I want to eventually deploy my website to Heroku. Website will be used by a group of people sharing the same network and printer. I do not know of a way to set heroku to communicate with the printer using this package.
I also thought that printing directly from the front end might be a better idea, but I have to open google on kiosk mode and then do the same for all the users that are going to use this website. Also, most of the users will be using a tablet device so configuring printer in those devices will be difficult as well.
I did not find anything online that I can use as a reference. Any advice or suggestion will be greatly appreciated.

As for nodeJs printing I have no experience. It seems that you can use certain packages to print a pdf as given in the example answer here: Node.js : How to add print job to printer.
As for generating from html to PDF, that should be easy to find, less easy to style correctly though.
I would recommend doing it from HTML (you could still do the PDF conversion for more stable printing results)
From HTML
As stated, the API is rather limited, you can use window.print to request a print action.
Note though that you have some options to make your life better when calling window.print().
You can create the page in a separate window to get rid of bloat, like navigation etc, or you could actually hide that with css.
You might already be aware of css being included for certain targets e.g. for your website you probably want to use the screen target, but you can create a separate stylesheet for printing.
More info at mozilla
https://developer.mozilla.org/en-US/docs/Web/Guide/Printing

Create hybrid desktop and web application with different languages

I want to create an app to estimate engineering costs: lots of tables, forms, a sidebar with a tree structure and so on. You can access a database in the cloud and create table structures according to records in the database.
Naturally that would be a website, however, if the user does not always have an access to the Internet, he/she can download a copy of that database (precisely, a copy of the current version of the database), so that it would be possible to get data from it and work locally. That is why an offline desktop app is needed.
Would it be possible to develop such a hybrid application without first creating a web app and then doing the same with a desktop app?
Previously i have looked into JavaFX, but we saw that it's too difficult to create a website out of that. Then we saw Electron, but i'm not sure if it is the right choice, because it seams that Electron is only used for desktop.

I'm lost as to why you feel you need a website/desktop hybrid. There are many APIs available to let you access a cloud database. All you have to do is find an API with web hooks, or APIs that specifically target the database type you are using (sql, mongo, or whatever). Then just cache a local copy once you've pulled down the database.
Work on the copy then push back to the database when they save, or try to do a push/pull every 5 minutes or something.

You can make a HTML page, which would:
Use AJAX calls if connected
Add relative <script> tag, thinking that HTML file lies in a folder on PC, and that script is somewhere nearbly.
In both cases, user will get same results.
Downloads are:
HTML file with inline script
JS file with database
or
zipped folder with HTML, database JS files and all scripts, images, css, etc. requred for HTML file to show properly.

PDF JS Functionality

I have created a HTML project. But my main aim is to display the pdf's on my site so that users can't save or download them is this possible using (https://mozilla.github.io/pdf.js/) viewer? If so how can i do it because i'm trying to output a lot of pdfs and this just seems impossible to do looking at the code.

No, it's not possible to display native pdfs to the user without allowing them to download them. By the nature of http, they will have had to download the pdf data in order for them to be displayed.
However, you could take snapshots of the pdf on the server, and display these to the user as pngs.
There are a number of libraries that will allow you to convert the first page of a pdf to an image, I suggest you start by trying to implement one of those.

PhoneGap - Read pre-packaged sqlite database

I've been struggling to get this working for too long. I just started to get into PhoneGap/Cordova. I got the demo app running, installed all official plugins, and added this SQLite plugin to begin work with: https://github.com/brodysoft/Cordova-SQLitePlugin
However, I want the plugin to read a pre-packaged database. Simply put, create an app that works offline and does not need to download an SQLite database when it is run for the first time.
I have been developing for Android for quite some time, and the solution was to deploy a read-only database file in the assets folder, and on first run copy the database file into a different folder, where I can read/write as I please.
So I did a little research and realized that it SHOULD be the same with PhoneGap. Place a binary SQLite database somewhere, so that when built, it will be packaged with the app. And then simply load it with the SQLite plugin I linked here.
Finally, the question! What are the exact steps I have to take to be able to read a file that was packaged with the app?
Where should I put my binary file to ensure that it gets packaged into the app?
How exactly should I initialize the File API? Should I ask for persistent storage using window.requestFileSystem? Or should I get some (not sure which) directory (cordova.file.applicationDirectory) as a DirectoryEntry using window.resolveLocalFileSystemURL? If so, what are the EXACT parameters I should use? I am mostly referring to this: https://github.com/apache/cordova-plugin-file/blob/master/doc/index.md
How do I read the packaged file? Using window.resolveLocalFileSystemURL with the right folder? What should then the parameters be?
File copying should work OK if I get to this point. Just copy from the read-only cordova.file.applicationDirectory into cordova.file.dataDirectory, which is read/write. Right?
I know the questions might be pretty basic, but my countless attempts were unsuccessful and I did not find a tutorial that explains this in-depth (believe me, I googled). Also, the documentation seems insufficient.
Just working with a WebSQL database and load data the DB using a s***load of INSERTs is not a viable option, the database has thousands of records.
Thanks for the help in advance, you will save me a headache or two.

Currently Cordova's standard SQLite Plugin supports Pre-populated Databases, which will copy your database file from www and put it into the right directory. It also supports Android as well as iOS, so you don't need to have different logic for different platforms.
When you open the database, you can specify that it is pre-populated using createFromLocation: 1 like this:
var db = window.sqlitePlugin.openDatabase({
name: "my.db",
createFromLocation: 1
});
For iOS, it will first check www and if the file exists, it will copy it to Documents. Keep in mind that it will be backed up by iCloud. If you want to exclude it from iCloud, then add location: 2 on openDatabase as well, which will put your databases in Library/LocalDatabase.
UPDATE (2016)
The original Cordova-sqlite-storage project does not support pre-populated db anymore.
However, this feature just moved to another project from the same creator. Now, use Cordova-sqlite-ext for this purpose.