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How to store and make changes to a database within a Chrome Extension?

I'm currently working on a Chrome Extension which searches for specific content within webpages.
Now, my idea is to build a Database based on the correctness of this search result (which would be verified by the users), so it can be more accurate in these searches as the database grows. Kind of like a Machine Learning process I guess.
I'm fairly new to programming and I would like your advice on what are the best possible ways to do this.
Currently I just have JS/HTML/CSS, and it seems to me that I'm gonna need some other language.
A single CSV that the Extension could read/write would be enough for this, I think. Or something with SQL.
Thanks in advance!

You have to compose and post a CRUD command to a web server page (a server you own or you controll)
That page can be written in php, asp.net..
Web server page receive the CRUD command and run the relevant statement on your database via OBCD driver (or other similar driver)
Normally the web server page then responds, as a result of your post, with a message (text, xml, json) that makes you understand if the command has been successfully executed or not.
EDIT 04/30/2021 16:24 Rome Timezone
you say:
which would be verified by the users
what did you mean exactly?
more users together contributes to make the shared database better ?
or every single user contribute by itself to make his own database better ?
if one then my previous answer could be a good start point.
if two, forget my previos answer a think to build a indexedDB within your extension.

Read a csv or txt file through XMLHttpRequest is not a problem, but how do you thing to write the same file with the same tool (XHR) ?
You could think about a Google public spreadsheet.
"Google Sheets" allows you through an "endpoint url" and a set of API to insert new rows\records and to read the entire content of the spreadsheet
or (if I remember correctly) part of its content.
I state that it's now 2 years or maybe more since I got interested in Google Sheets.
Based on the information in my possession, perhaps outdated,
I can tell you that "Google Sheets" it is a path that I DO NOT advise you to follow.
First, because spreadsheet url being public would allow an attacker to pollute your DB by inserting many rows\records
by simply typing a url in the browser's address bar or creating a simple bot that inserts thousands of lines in a while.
Second, because that set of API do not allow you to implement very sophisticated queries (certainly not at the database level).
If you are really interested in Google Sheets I suggest you check what I have just stated.
If you have to "waste" energy to learn something new
I would suggest you to give priority to SQL and then to a server-side programming language (php, asp.net, node.js)
However, a free space hosting service with php and mySQL support is not too difficult to find.

Are string saved to arrays permanently saved?

I'm an 11-year-old learning how to code Javascript, I recently started 1 and a half months ago. I am making a login/register system and am trying to make the register part now. I was wondering if adding a string/number/boolean to an array stays there forever (even after refresh). I would've used cookies for this, but it is not safe.
I am currently using HTML5, CSS3, Javascript, and eventually will be using Jquery. NOTE: The time period does not have to be forever. Does any know the answer to this, please reply?
P.S. ( iff you mention PHP for this there would be no point, I don't understand it yet. :/ )

The answer is no. Note that anytime you reload a browser page, your JavaScript also reloads with the page.
If you want you data to persist, use a database.

a string or whatever you have in an array will not stay in it forever simply because an array is a data structure which is not persistent. Since you have it in your intention to use more advanced technologies in the near future and you are not comfortable with the cookie because of the obvious security risks. I suggest you use a localStorage to implement the registration feature for your app. Of course you can achieve the same with a sessionStorage, however whatever you save in a sessionStorage will be wiped off when you close the tab which can be handy in the implementation of you login and logout feature for now. Whenever you upgrade the applications to more sophisticated technologies you will have a better way to handle those features.
PS: it might be a little advanced for you right now but when you are more comfortable writing Javascript maybe you will like to checkout IndexDB then NodeJs very much later.
#cheers #dontRelent

If you want to create login functionality, you will have to start learning some server-side technologies.
When I was finished (kind of) with learning JavaScript i moved on to NodeJS and MongoDB. NodeJS allows you use JavaScript on the server-side and MongoDB is a database program where you could store data.
Using those two you would create a user model, store it and then check if the user is logged in and etc.
There are many choices to go with when learning back-end, I went with NodeJS because as I already knew JavaScript it was easier to use the same language for the back-end. That and it was part of the Udemy course I had.
Good luck.

It depends on where you're storing that array. If you want to make a functional login/register on a web-page, you will likely need to use a database such as PostgreSQL.
However, if you want to just create a simple program to run on the command line, the username or password strings you enter in will not remain in memory if you terminate the program. If you terminate your program, it will delete the strings added to your array.

Looking for ways to aggregate info/data from different websites

I'm a fresh-out-of-college programmer with some experience in Python and Javascript, and I'm trying to develop either a website or just a back-end system that will aggregate information from online market websites which don't have any API (or none that I've found, anyway). Ideally I would also want the system that can write to local storage to track changes to the data over time in some kind of database, but that's down the road a bit.
I've already pounded out some javascript that can grab the data I want, but apparently there doesn't seem to be a way to access or act upon data from other websites due to data security protections or to save the data to local storage in order to be read from other pages. I know that there are ways to aggregate data, as I've seen other websites that do this.
I can load websites in Python using the urllib2 and use regular expressions to parse what I want from some pages, but on a couple of the desired sites I would need to log into the website before I can access the data I want to gather.
Since I am relatively new to programming, is there an ideal tool / programming language that would streamline or simplify what I'm trying to do?
If not, could you please point me in the right direction for how I might go about this? After doing some searching, there seems to be a general lack of cross-domain data gathering and aggregation. Maybe I'm not even using the right terminology to describe what I'm trying to do.
Whichever way you would look at this, please help! :-)

i suggest you use selenium webdriver to login to get cookie,and use requests library to scrap the message.That is what my company do in the scraping system.if you only use selenium webdriver, you will need to many memory and cpu capacity.
if you are good at html and js,it is a good way for you to use requests library to Simulate logging.
for the website you must log in,the most import thing is to get cookie.

Is a database required for a "quiz" type of game?

I don't know much about databases, I've been asking a few questions about them lately to get a better understanding but I'm still a bit confused about what does and doesn't need one.
I'm making a simple application using HTML/CSS/JavaScript, it has a few quizzes and "tutorials" targeted towards children. I don't want the next tutorial/quiz to be unlocked until the previous one is completed.
So for that would I need a database so that it "saves" when one is completed? I don't need to save scores or anything like that, they just get to move on once they get a passing score.

Any other requirements such as saving to a profile or needing to persist between sessions (e.g. changing of device)?
Browsers have localStorage APIs now which allow you to save a lot of the data (and keep it for a set duration of time). There are also good'ol'fashioned cookies which allow you save pieces of information as well.
Keep in mind that both of the above mandate the user use the same browser and allow these mechanisms. Obviously using "private"/"incognito" browsing would also affect saving status.
It's up to what you feel the requirements are.
EDIT Just saw your mention of a mobile app. If you're planning on allowing the experience to transcend devices, you'll need a database. otherwise, you'll be relying heavily on if they use cross-device sync (like Chrome and Firefox do with bookmarks, passwords, etc.)

If you don't mind that people can do a "view source" on the webpage or use every browsers' developer tools to find out the answers or move on to the next tutorial or quiz, then you can use cookies to store the user's status. Or you can use the preferable Web Storage API.
You might want to look at Firebase. Using just simple JavaScript on the web browser, you can have users with logins (or just allow them to login via Facebook or other services) very easily. And then you can store and retrieve data very easily as well, like quizzes, tutorials and results. This way nobody can see the answers even if they're adept at analyzing the webpage.

When you don't use database, before any check, you have to load all data in your static page.
So My sloution: store students situation in a cookie. On each page check cookie status and then use Jquery remove() to remove (Client-side) those parts of page that he/she can not access.
EDIT
This wont work when JavaScript is disabled.

There seems to be a lot of ideas but no clarifying on the database subject.
TL;DR is: No.
Now for the specifics. A database is nothing more than a way to store information. While traditional "SQL" databases (it is pronounced "Sequel" as in "My Sequel" for MySQL) have concepts of tables, where you define columns with items to store and saves each row with its value, much like an Excel file, some databases like Redis store key-value pairs and others lide MongoDB store JavaScript Objects.
You can store information in the source code (As Variables possibly) or in a file. A database is a way to organize that information.
With that said, in your case, you probably need a backend or an API. An API is basically a means of communication with a server through AJAX (JavaScript in the browser asks for stuff). That would be your way to retrieve information from the server as needed, so that users wouldn't see the answers before they answer.
With that out of the way, there are some options. FireBase (As noted on other answer) and AppBase are easy ways to integrate this concept with little effort. But they tie you and your information to their system, and they are mostly targeting more resource intensive apps.
Since you are using JS and seem to be enjoying your learning experience, I would suggest you consider suing NodeJS and defining the data as either a JSON file or a variable in JS. You keep working on your problem but add options and get to learn some stuff.
If you decide to integrate a database and possibly do some neat stuff, you have most of the groundwork done already.
If NodeJS picks your interest, Mean.IO and KrakenJS are, in my opinion, the best places to start, though they may both seem overkill in your specific case.
Do consider though: A database is just a small possible piece in a puzzle, and it's mostly a horrible way to name some of the software that tries to organize your information. Consider first if you need to organize information, and what and how do you need to organize, then start thinking if databases are the best way to organize it.

Google Gadget, Javascript (Or Other) Way To Port Collected Data

I am working on a Google Gadget that will collect some data through Google API's. What I am getting stuck on is how to collect the data and then save it somewhere to be processed later. The final idea being that I would run the gadget on my own computer it would collect the data and then save it to somewhere on my own computer. (I guess I want to emphasize that this is, for now, a small personal project and does not necessarily need fancy server scripts, I want to be able to run this all on my PC running XP).
Is there a pure Javascript way to save a file on a computer?
Can I use other languages besides XML, HTML, and Javascript to add functionality to my Google Gadget?
Edit: The goal of this is to be able to log how many of my contacts are signed into gchat over a period of time. I decided on a Gadget because that was the only way I could figure out how to access that information. Any other ways to approach this idea are welcome!

No, Javascript alone cannot save a file automatically. And be careful, javascript is affected by the no cross domain rule. If you're hosting the project on your own computer, why bother writing a complex Google Gadget?
I suggest a simple PHP script, and MySQL, if you like, to store the data. By itself, PHP should be more than enough to run most tasks. If you would like me to add in more info about this, please tell me what type of task.

In increasing order of flexibility:
The options object is almost certainly the easiest approach - not really designed for that kind of usage but I suspect it would be fine for your use case.
On windows you could use system.filesystem to get hold of the WScript FileSystemObject which you can then use to create files and write to them.
Also see the Google desktop API blog for embedding an SQLite database in your gadget (looks pretty easy).