const powerset = arr =>
  arr.reduce((a, v) => a.concat(a.map(r => r.concat(v))), [[]]);
  
powerset([1, 2]); // [[], [1], [2], [1, 2]]

// `date` is a `Date` object
const formatYmd = date => date.toISOString().slice(0, 10);

// Example
formatYmd(new Date());      // 2020-05-06

// Vanilla JS Solution:
var app = document.getElementById('app');

var typewriter = new Typewriter(app, { loop: true });

typewriter
    .typeString("I'm John and I'm a super cool web developer")
    .pauseFor(3000)
    .deleteChars(13) // "web developer" = 13 characters
    .typeString("person to talk with!") // Will display "I'm John and I'm a super cool person to talk with!"
    .start();

// React Solution:
import Typewriter from 'typewriter-effect';

<Typewriter
    options={{ loop: true }}
    onInit={typewriter => {
        typewriter
            .typeString("I'm John and I'm a super cool web developer")
            .pauseFor(3000)
            .deleteChars(13) // "web developer" = 13 characters
            .typeString("person to talk with!") // Will display "I'm John and I'm a super cool person to talk with!"
            .start();
    }}
/>

const MongoClient = require('mongodb').MongoClient;
const assert = require('assert');

// Connection URL
const url = 'mongodb://localhost:27017';

// Database Name
const dbName = 'myproject';

// Use connect method to connect to the server
MongoClient.connect(url, function(err, client) {
  assert.equal(null, err);
  console.log("Connected successfully to server");

  const db = client.db(dbName);

  client.close();
});

//JavaScript program to swap two variables

//take input from the users
let a = prompt('Enter the first variable: ');
let b = prompt('Enter the second variable: ');

//using destructuring assignment
[a, b] = [b, a];

console.log(`The value of a after swapping: ${a}`);
console.log(`The value of b after swapping: ${b}`);

// Or
const randomColor = () => `#${(~~(Math.random()*(1<<24))).toString(16)}`;
console.log(randomColor);