osamaimran25 / carma-test

Node Version

v16.14.2

Setup project

npm install

Encryption

For encryption I have use cipher of Node js crypto with ""aes-256-cbc"" Algorithan which widely used for encryption and consider as more safe and easy to handle.

Luhn algorithm

I use https://www.npmjs.com/package/luhn-js for validating the card number it is easy to use and give you different methods

Question# 01

for (var i = 0; i < 100; i++) {
setTimeout(function() {
console.log(i);
}, 200);

}

OUTPUT:
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100

Reason:
the calls to setTimeout() — take almost no time at all. which is telling the system,  call this function after 200 milliseconds" 
will return almost immediately, as the process of installing the timeout request in the timer queue is very fast.

Question# 02

(async function() {
function waitForMe() {
return new Promise(function(resolve, reject) {
setTimeout(function() {
resolve("hello");
}, 200);
});
}
const result = await waitForMe();
console.log(result);
})();

// it is an IIFE.
OUTPUT:
hello

Question# 03

to entire function.
let b;// it is a use to declare block scope variable it doesnt declare globally in other words it is use to declare variable to an expression or block.
const c; // it is use to declare a variable to define a variable which value do not change over the program 

Question# 03

var arr = [];
module.exports = arr;

We got a module using it: // module 01
var test = require("./test");
test.push("hello");
console.log(JSON.stringify(test));

We got another module using it later:// moduule 02
var test = require("./test");
test.push("another");
console.log(JSON.stringify(test));

OUTPUT:

 in module 2 we get ["another"] because each module use it own instance for a test.js modeule ```