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How to get data from back end side, to use it in the browser side?

I am new to programming, and I heard that some guys on this website are quite angry, but please don't be. I am creating one web app, that has a web page and also makes som ecalculations and works with database (NeDB). I have an index.js
const selects = document.getElementsByClassName("sel");
const arr = ["Yura", "Nairi", "Mher", "Hayko"];
for (let el in selects) {
for (let key in arr) {
selects[el].innerHTML += `<option>${arr[key]}</option>`;
}
}
I have a function which fills the select elements with data from an array.
In other file named: getData.js:
var Datastore = require("nedb");
var users = new Datastore({ filename: "players" });
users.loadDatabase();
const names = [];
users.find({}, function (err, doc) {
for (let key in doc) {
names.push(doc[key].name);
}
});
I have some code that gets data from db and puts it in array. And I need that data to use in the index.js mentioned above, but the problem is that I don't know how to tranfer the data from getData.js to index.js. I have tried module.exports but it is not working, the browser console says that it can't recognize require keyword, I also can't get data directly in index.js because the browse can't recognize the code related to database.

You need to provide a server, which is connected to the Database.
Browser -> Server -> DB
Browser -> Server: Server provides endpoints where the Browser(Client) can fetch data from. https://expressjs.com/en/starter/hello-world.html
Server -> DB: gets the Data out of the Database and can do whatever it want with it. In your case the Data should get provided to the Client.
TODOs
Step 1: set up a server. For example with express.js (google it)
Step 2: learn how to fetch Data from the Browser(Client) AJAX GET are the keywords to google.
Step 3: setup a Database connection from you Server and get your data
Step 4: Do whatever you want with your data.

At first I thought it is a simple method, but them I researched a little bit and realized that I didn't have enough information about how it really works. Now I solved the problem, using promises and templete engine ejs. Thank you all for your time. I appreciate your help)

Save data from GET request as variable

I've got a simple axios GET request that is working with Azure directline 3.0. The GET request pulls back data and shows it in the console (as seen in the picture).
The data I want to save into a variable is the conversationId. I then want to use this variable with Axios Post in another JS file to post as part of the link e.g. let URL = "https://directline.botframework.com/v3/directline/conversations/"+convID"/activities". With convID being the variable I wish to create. Right now I am manually changing the convID with the new conversation ID, but I want to create a variable so I can place it in the post javascript file so it is automatic.enter image description here

There are various ways you can solve this problem. Easiest one being, exposing the data on a shared object window.convID = convID and then accessing it wherever required.
You could also look to make singleton objects, which can be instantiated only once and hence will share it's variables across the lifespan of the application.
axios.get(/* URL */).then(res => {
window.convID = res.data.conversationId;
});

You can save that variable value in LocalStorage. Something like this:
let routeToYourApi = '/api/conversations'; // or something like this...
axios.get(routeToYourApi).then((response) => {
let conversationId = response.data.conversationId; // not sure if data object from your image is directly nested inside response that you get from server, but you get the idea...
window.localStorage.setItem("convId", conversationId);
}) // here you can fetch your conversation id
Than you can access it anywhere in your app:
let conversationId = window.localStorage.getItem("convId");
... and eventually remove it from local storage:
window.localStorage.removeItem("convId")
Hope this will help you!

Express with JSON Data Control

I use lowDB dependency to control the JSON Data with Express and actually it works. But there is a bug and I cannot find how to solve it.
I create /create page to add information in JSON file and it contains 4 form and submit button.
And In express I code like this. each forms data will save it in variable and push with lowdb module.
router.post('/post', function (req, res) {
let pjName = req.body.projectName;
let pjURL = req.body.projectURL;
let pjtExplanation = req.body.projectExplanation;
let pjImgURL = req.body.projectImgURL;
console.log(pjName);
db.get('project').push({
name: pjName,
url: pjURL,
explanation: pjtExplanation,
imgurl: pjImgURL
}).write();
console.log(db.get('project'));
console.log(db.get('project').value());
res.redirect('/');
})
And it works well. But when I modify the JSON file myself (ex. reset the JSON file) and execute again. It shows the data that I reset before. I think in this app somewhere saves the all data and show save it in array again.
And When I shutdown the app in CMD and execute again, the Array is initialized.

As you may already know the lowdb persist the data into your secondary memory (hdd), and may return a promise depending on your environment when you call write method.As mentioned in the doc
Persists database using adapter.write (depending on the adapter, may return a promise).
So the data may be still getting write when you read them, so the old data is queried. Try this,
db.get('project').push({
name: pjName,
url: pjURL,
explanation: pjtExplanation,
imgurl: pjImgURL
}).write().then(() => {
console.log(db.get('project'));
console.log(db.get('project').value());
});

Parse iOS SDK: Understanding Cloud Code

Scenario = I am slowly but surely wrapping my head around what is going on with Parse's cloud code features. I just need some help from those who would like to answer some short, relatively simple questions about what is going on in some sample cloud code functions.
The code I will use in this example is below
1) cloud code
Parse.Cloud.define('editUser', function(request, response) {
var userId = request.params.userId,
newColText = request.params.newColText;
var User = Parse.Object.extend('_User'),
user = new User({ objectId: userId });
user.set('new_col', newColText);
Parse.Cloud.useMasterKey();
user.save().then(function(user) {
response.success(user);
}, function(error) {
response.error(error)
});
});
2) called from iOS
[PFCloud callFunction:#"editUser" withParameters:#{
#"userId": #"someuseridhere",
#"newColText": #"new text!"
}];
This code was taken from here
Question 1 =
(request, response)
I am confused by what this is. Is this like typecasting in iOS where I am saying (in the iOS call) I want to pass an NSString into this function ("userId") and inside the cloud code function I'm going to call it "request"? Is that what's going on here?
Question 2 =
Parse.Object.extend('_User')
Is this grabbing the "User" class from the Parse database so that a "PFObject" of sorts can update it by creating a new "user" in the line below it?
Is this like a...
PFObject *userObject = [PFObject objectWithClassName:#"User"]?
Question 3 =
user.set('new_col', newColText)
This obviously 'sets' the values to be saved to the PFUser (~I think). I know that the "newColText" variable is the text that is to be set - but what is 'new_col'? Only thing I can think of is that this sets the name of a new column in the database of whatever type is being passed through the "request"?
Is this like a...
[[PFUser currentUser] setObject: forKey:]
Question 4 =
Parse.Cloud.useMasterKey()
Without getting too technical, is this basically all I have to type before I can edit a "User" object from another User?
Question 5 =
user.save().then(function(user) {
response.success(user);
}
Is this like a...
[user saveInBackgroundWithBlock:]?
and if so, is
function(error) {
response.error(error)
just setting what happens if there is an error in the saveInBackgroundWithBlock?
Please keep in mind, I know iOS - not JavaScript. So try to be as descriptive as possible to someone who understands the Apple realm.

Here's my take on your questions:
The request parameter is for you to access everything that is part of the request/call to your cloud function, it includes the parameters passed (request.params), the User that is authenticated on the client (request.user) and some other things you can learn about in the documentation. The response is for you to send information back to the calling code, you generally call response.success() or response.error() with an optional string/object/etc that gets included in the response, again documentation here.
That's a way of creating an instance of a User, which because it is a special internal class is named _User instead, same with _Role and _Installation. It is creating an instance of the user with an ID, not creating a new one (which wouldn't have an ID until saved). When you create an object this way you can "patch" it by just changing the properties you want updated.
Again, look at the documentation or an example, the first parameter is the column name (it will be created if it doesn't exist), the second value is what you want that column set to.
You have to do Parse.Cloud.useMasterKey() when you need to do something that the user logged into the client doesn't have permission to do. It means "ignore all security, I know what I'm doing".
You're seeing a promise chain, each step in the chain allows you to pass in a "success" handler and an optional "error" handler. There is some great documentation. It is super handy when you want to do a couple of things in order, e.g.
Sample code:
var post = new Parse.Object('Post');
var comment = new Parse.Object('Comment');
// assume we set a bunch of properties on the post and comment here
post.save().then(function() {
// we know the post is saved, so now we can reference it from our comment
comment.set('post', post);
// return the comment save promise, so we can keep chaining
return comment.save();
}).then(function() {
// success!
response.success();
}, function(error) {
// uh oh!
// this catches errors anywhere in the chain
response.error(error);
});

I'm pretty much at the same place as you are, but here are my thoughts:
No, these are the parameters received by the function. When something calls the editUser cloud function, you'll have those two objects to use: request & response. The request is basically what the iOS device sent to the server, and response is what the server will send to the iOS device.
Not quite that. It's like creating a subclass of _User.
Think of Parse objects types as a database table and it's instances as rows. The set will set (derp) the value of 'newColText' to the attribute/column 'new_col'.
Not sure, never used that function as I don't handle User objects. But might be that.
Pretty much that. But it's more sort of like (pseudo-code, mixing JS with Obj-C):
[user saveInBackgroundWithBlock:^(BOOL succeeded, NSError *error){
if(error){
response.error(error); // mark the function as failed and return the error object to the iOS device
}
else{
response.success(user); // mark the function call as successful and return the user object to the iOS device
}
}];

InDesign scripting of the Socket object yields cryptic error message

I'm working on a broadcast e-mail template that would pull the latest three articles off our blog from an RSS feed and insert the relevant sections into the document.
I looked at the documentation, and based on the bit about the File object, some of my own debugging, and an InDesign forum post I've learned that it's not possible to use the File object to source an online XML file.
The alternative (without resorting to an external script, one of which didn't work for me anyways), it seems, is to use the Socket object. So I went back to the documentation and copied/pasted this code verbatim from there:
reply = "";
conn = new Socket;
// access Adobe’s home page
if (conn.open ("www.adobe.com:80")) {
// send a HTTP GET request
conn.write ("GET /index.html HTTP/1.0\n\n");
// and read the server’s reply
reply = conn.read(999999);
conn.close();
}
When I ran it, I received this descriptive error message:
A search for "89858 javascript error" yielded nothing useful.
So I'm stuck. Either Adobe's code sample has an error, or, more likely, there's something wrong on my end. If I had to guess, I'd guess that it's some kind of proxy problem, but I don't know for sure and don't know how to find out.
Can anyone help? The principles of the Socket object make sense to me, but if I can't get even the sample to work, I don't really have anywhere to go with this.

The error above occurs when you return certain objects (XML, Socket) from a function call, but the return values does not get assigned anywhere.
function test() {
var xml = new XML('<test />');
return xml;
}
test();
The above will cause an error. To get around it you have to assign the return value somewhere.
var result = test();
Try to put all collect all function calls result. I am not sure which one causes the error.
var reply = "";
var conn = new Socket;
// access Adobe’s home page
if (conn.open ("www.adobe.com:80")) {
// send a HTTP GET request
var result = conn.write ("GET /index.html HTTP/1.0\n\n");
// and read the server’s reply
reply = conn.read(999999);
var close = conn.close();
}