const luhnCheck = num => {
  let arr = (num + '')
    .split('')
    .reverse()
    .map(x => parseInt(x));
  let lastDigit = arr.splice(0, 1)[0];
  let sum = arr.reduce(
    (acc, val, i) => (i % 2 !== 0 ? acc + val : acc + ((val *= 2) > 9 ? val - 9 : val)),
    0
  );
  sum += lastDigit;
  return sum % 10 === 0;
};

luhnCheck('4485275742308327'); // true
luhnCheck(6011329933655299); //  true
luhnCheck(123456789); // false

const flat = arr => [].concat.apply([], arr.map(a => Array.isArray(a) ? flat(a) : a));
// Or
const flat = arr => arr.reduce((a, b) => Array.isArray(b) ? [...a, ...flat(b)] : [...a, b], []);

// Or
// See the browser compatibility at https://caniuse.com/#feat=array-flat
const flat = arr => arr.flat();

// Example
flat(['cat', ['lion', 'tiger']]);   // ['cat', 'lion', 'tiger']

import React, { useState, useEffect } from 'react';
import Link from 'next/link';

export default function CookieBanner() {
    // Initialize with a default value (false if not previously set in localStorage)
  const [cookieConsent, setCookieConsent] = useState(() =>
    localStorage.getItem('cookieConsent') === 'true' ? true : false
  );

  useEffect(() => {
    const newCookieConsent = cookieConsent ? 'granted' : 'denied';

    window.gtag('consent', 'update', {
      analytics_storage: newCookieConsent
    });

    localStorage.setItem('cookieConsent', String(cookieConsent));
  }, [cookieConsent]);

  return !cookieConsent && (
    <div>
    <div>
        <p>
        We use cookies to enhance the user experience.{' '}
        <Link href='/privacy/'>View privacy policy</Link>
        </p>
    </div>
    <div>
        <button type="button" onClick={() => setCookieConsent(false)}>Decline</button>
        <button type="button" onClick={() => setCookieConsent(true)}>Allow</button>
    </div>
    </div>
  )
}

import { configureStore } from "@reduxjs/toolkit";
import { combineReducers } from "redux";
import profile from "./profile";
import auth from "./auth";
import alert from "./alert";

const reducer = combineReducers({
	profile,
	auth,
	alert,
});

const store = configureStore({ reducer });

export default store;

const express = require('express')
const app = express()
const port = 3000

app.get('/', (req, res) => {
  res.send('Hello World!')
})

app.listen(port, () => {
  console.log(`Example app listening on port ${port}`)
})

const kMeans = (data, k = 1) => {
  const centroids = data.slice(0, k);
  const distances = Array.from({ length: data.length }, () =>
    Array.from({ length: k }, () => 0)
  );
  const classes = Array.from({ length: data.length }, () => -1);
  let itr = true;

  while (itr) {
    itr = false;

    for (let d in data) {
      for (let c = 0; c < k; c++) {
        distances[d][c] = Math.hypot(
          ...Object.keys(data[0]).map(key => data[d][key] - centroids[c][key])
        );
      }
      const m = distances[d].indexOf(Math.min(...distances[d]));
      if (classes[d] !== m) itr = true;
      classes[d] = m;
    }

    for (let c = 0; c < k; c++) {
      centroids[c] = Array.from({ length: data[0].length }, () => 0);
      const size = data.reduce((acc, _, d) => {
        if (classes[d] === c) {
          acc++;
          for (let i in data[0]) centroids[c][i] += data[d][i];
        }
        return acc;
      }, 0);
      for (let i in data[0]) {
        centroids[c][i] = parseFloat(Number(centroids[c][i] / size).toFixed(2));
      }
    }
  }

  return classes;
};
kMeans([[0, 0], [0, 1], [1, 3], [2, 0]], 2); // [0, 1, 1, 0]