const insertionSort = arr =>
  arr.reduce((acc, x) => {
    if (!acc.length) return [x];
    acc.some((y, j) => {
      if (x <= y) {
        acc.splice(j, 0, x);
        return true;
      }
      if (x > y && j === acc.length - 1) {
        acc.splice(j + 1, 0, x);
        return true;
      }
      return false;
    });
    return acc;
  }, []);
  
insertionSort([6, 3, 4, 1]); // [1, 3, 4, 6]

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 head = arr => (arr && arr.length ? arr[0] : undefined);

head([1, 2, 3]); // 1
head([]); // undefined
head(null); // undefined
head(undefined); // undefined

const formatDuration = ms => {
  if (ms < 0) ms = -ms;
  const time = {
    day: Math.floor(ms / 86400000),
    hour: Math.floor(ms / 3600000) % 24,
    minute: Math.floor(ms / 60000) % 60,
    second: Math.floor(ms / 1000) % 60,
    millisecond: Math.floor(ms) % 1000
  };
  return Object.entries(time)
    .filter(val => val[1] !== 0)
    .map(([key, val]) => `${val} ${key}${val !== 1 ? 's' : ''}`)
    .join(', ');
};

formatDuration(1001); // '1 second, 1 millisecond'
formatDuration(34325055574); // '397 days, 6 hours, 44 minutes, 15 seconds, 574 milliseconds'

const binomialCoefficient = (n, k) => {
  if (Number.isNaN(n) || Number.isNaN(k)) return NaN;
  if (k < 0 || k > n) return 0;
  if (k === 0 || k === n) return 1;
  if (k === 1 || k === n - 1) return n;
  if (n - k < k) k = n - k;
  let res = n;
  for (let j = 2; j <= k; j++) res *= (n - j + 1) / j;
  return Math.round(res);
};

binomialCoefficient(8, 2); // 28

import React, { useState } from 'react' import Welcome from '../components/Welcome'  function About() {  	const [showWelcome, setShowWelcome] = useState(false)  	return ( 	<div> 	{showWelcome ? <Welcome /> : null} 	</div> 	<div> 	{showWelcome && <Welcome /> } 	</div> 	) }  export default App