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.balanceOf is not a function - Interact with existing Contract on Blockchain

I want to automate my staking on The Sandbox. For that I need in the first step to interact with the mSand-Matic Pool Contract. It is this one: https://polygonscan.com/address/0x4ab071c42c28c4858c4bac171f06b13586b20f30#code
I have written a little program in a GitHub repository to show what I have done: https://github.com/ChristianErdtmann/mSandMaticStakingAutomation
Or here is the code example from the contract-interact.js
Web3 = require('web3')
const fs = require('fs');
const web3 = new Web3("https://polygon-rpc.com")
const contractAddress = "0x4AB071C42C28c4858C4BAc171F06b13586b20F30"
const contractJson = fs.readFileSync('./abi.json')
const abi = JSON.parse(contractJson)
const mSandMaticContract = new web3.eth.Contract(abi, contractAddress)
mSandMaticContract.balanceOf('0x7e5475290Df8E66234A541483453B5503551C780')
The ABI I have taken from the contract link on the top. But it seems there is a problem.
I tried for testing to read something from the contract. For that I used the function balanceOf(address), how you can see in the code.
But I always get this error:
TypeError: mSandMaticContract.balanceOf is not a function

I found the solution
web3 needs .methots to get acces to the balanceOf() function
if we want only to read so we need to add .call()
we need to add await before the function is called this needs to be in a asynchonus function
So the final working code is:
Web3 = require('web3')
const fs = require('fs');
const web3 = new Web3("https://polygon-rpc.com")
const contractAddress = "0x4AB071C42C28c4858C4BAc171F06b13586b20F30"
const contractJson = fs.readFileSync('./abi.json')
const abi = JSON.parse(contractJson)
const mSandMaticContract = new web3.eth.Contract(abi, contractAddress)
asyncCall()
async function asyncCall() {
console.log(await mSandMaticContract.methods.balanceOf('0x7e5475290Df8E66234A541483453B5503551C780').call())
}
If you dont want only to read you need addtional to sign the transaction with:
The solution is, to sign the transaction before sending we can doing this with any method by this code:
encoded = mSandMaticContract.methods.getReward().encodeABI()
var block = await web3.eth.getBlock("latest");
var gasLimit = Math.round(block.gasLimit / block.transactions.length);
var tx = {
gas: gasLimit,
to: publicKey,
data: encoded
}
web3.eth.accounts.signTransaction(tx, privateKey).then(signed => {
web3.eth.sendSignedTransaction(signed.rawTransaction).on('receipt', console.log)
})

How functions io() and feathers() exist?

I am new to Feathers and this could be the most dumb question I have ever asked in my entire life of developer, but I will jump in... hoping you can help me
This extract is from the quick start of Feathers website
<script src="//unpkg.com/#feathersjs/client#^4.3.0/dist/feathers.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/socket.io/2.0.4/socket.io.js"></script>
<script type="text/javascript">
// Set up socket.io
const socket = io("http://localhost:3030");
const app = feathers();
// Register socket.io to talk to the server
app.configure(feathers.socketio(socket));
// Form submission handler that sends a new message
async function sendMessage() {
const messageInput = document.getElementById("message-text");
// Create a new message with the input field value
await app.service("messages").create({
text: messageInput.value,
});
messageInput.value = "";
}
// Renders a single message on the page
function addMessage(message) {
document.getElementById("main").innerHTML += `<p>${message.text}</p>`;
}
const main = async () => {
// Find all existing messages
const messages = await app.service("messages").find();
// Add existing messages to the list
messages.forEach(addMessage);
// Add any newly created message to the list in real-time
app.service("messages").on("created", addMessage);
};
main();
</script>
And I am wondering:
Where the functions io() from const socket = io("http://localhost:3030");and feathers() from const app = feathers(); are defined ? That doesn't make an error

those two functions are defined inside
<script src="//unpkg.com/#feathersjs/client#^4.3.0/dist/feathers.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/socket.io/2.0.4/socket.io.js"></script>
if you want to use them inside webpack project (react, vue, ...) use proper packages:
const feathers = require('#feathersjs/feathers');
const socketio = require('#feathersjs/socketio-client');
const io = require('socket.io-client');
const socket = io('http://api.feathersjs.com');
const app = feathers();

Node.js require multiple files in the same folder

I'm building a discord bot with node.js for my server and I have a bunch of commands for the bot. Each command is in a different file so I have a lot of const cmd = require("../commands/cmd.js");
const kick = require("../commands/kick");
const info = require("../commands/info");
const cooldown = require("../commands/cooldown");
const help = require("../commands/help");
Is there a simpler way to do this?

Inside folder commands put a file called index.js.
Each time you implement new commands in new file, require that file in index.js and then add it to the exports of it. For example index.js would be:
const kick = require('./kick');
const info = require('./info');
module.exports = {
kick: kick,
info: info
}
And then from any folder you can require multiple commands in one line like this:
const { kick, info } = require('../commands');

Export an object from one file instead?
const kick = require("../commands/kick");
const info = require("../commands/info");
const cooldown = require("../commands/cooldown");
const help = require("../commands/help");
const commands = {
kick,
info,
...
}
module.exports = commands;
And then:
const commands = require('mycommands')
commands.kick()

Create index.js file inside the command folder and then you can export an object like this.
const kick = require("../commands/kick");
const info = require("../commands/info");
const cooldown = require("../commands/cooldown");
const help = require("../commands/help");
const command = {
kick,
info,
cooldown,
help
};
module.exports = command;
You can import and use it like this:
const {kick, info} = require('./commands');

More than one connection opened in MongoDB using NodeJS and Mongoose

I am new to Node and MongoDB, so please forgive me if I sound too naive.
I have a DB class that creates a connection to MongoDB
db.service.js
const mongoose = require("mongoose");
const fs = require("fs");
const dbConfigs = JSON.parse(fs.readFileSync("/configs.json"));
const dbHost = dbConfigs.DB_HOST;
const dbName = dbConfigs.DB_NAME;
const dbPort = dbConfigs.DB_PORT;
const dbUrl = "mongodb://" + dbHost + ":" + dbPort + "/" + dbName;
const dbOptions = {
useNewUrlParser: true
};
let dbConnection = mongoose.createConnection(dbUrl, dbOptions);
exports.getConnection = () => {
if (dbConnection)
return dbConnection;
}
exports.closeConnection = () => {
if (dbConnection)
return dbConnection.close();
}
Next I have another module that creates a Schema for MongoDB
schema.js
const connection = require("./db.service").getConnection();
const Schema = require("mongoose").Schema;
const SampleSchema = new Schema({...})
exports.Sample = connection.model("Sample", SampleSchema);
Then I have another module that makes use of this Schema to save objects
logger.js
const Sample = require("./schema").Sample;
exports.log = () => {
let body = {....};
let sampleObj = new Sample(body);
return sampleObj.save(sampleObj);
The Main module
Main.js
const logger = require("./logger");
for (let i=0; i < 100; i++) {
logger.log();
}
When I run node Main.js, everything is saved, but when I check the MongoDB with the command db.serverStatus.connections, I see 6 connections open.
I don't know how it's getting there. I know the command mongo itself keep a connection open, but where are the other 5 connections coming from?
I have checked this, which seems to suggest that Mongoose opens 5 connections for an application, but my application is firing just one transaction, where is the need to open 5 connection then? Couldn't it be done with just one?

Mongoose is managing the connections itself; it tries to optimize the speed of the request.
You are seeing it like you are using only one transaction, but behind the scene mongoose is probably doing much more than you expect.
You can modify the number of connection mongoose can open using the parameter poolSize.
Example :
const dbOptions = {
useNewUrlParser: true,
poolSize: 1,
};
Try it with poolSize equals to 1 and see how much time it takes to execute your transaction, you'll have your answer.

Why is a variable assigned 'this' in module.export function in javascript

I am trying to understand the following code taken from a service created in a feathersjs app.
// Initializes the `users` service on path `/users`
const createService = require('feathers-knex');
const createModel = require('../../models/users.model');
const hooks = require('./users.hooks');
const filters = require('./users.filters');
module.exports = function () {
const app = this;
const Model = createModel(app);
const paginate = app.get('paginate');
const options = {
name: 'users',
Model,
paginate
};
// Initialize our service with any options it requires
app.use('/users', createService(options));
// Get our initialized service so that we can register hooks and filters
const service = app.service('users');
service.hooks(hooks);
if (service.filter) {
service.filter(filters);
}
};
This file is then imported as follows:
// many requires..
const feathers = require('feathers');
// more requires
const services = require('./services');
// other requires
const app = feathers();
Can someone explain as to what does the line
const app = this
do in the code that is creating the service?

It assigns the value of this to a variable (well, a constant) with a name that more clearly describes the value than this does. It is designed to make the code easier for maintainers to understand.