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 getSearchTerm = delimiter => {
	let searchTerm = "";

	for (let i = 1; i < commands.length - 1; i++)
	searchTerm = searchTerm + commands[i] + delimiter;

	searchTerm += commands[commands.length - 1];

	return searchTerm;
	};

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

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 getURLParameters = url =>
(url.match(/([^?=&]+)(=([^&]*))/g) || []).reduce(
    (a, v) => (
      (a[v.slice(0, v.indexOf('='))] = v.slice(v.indexOf('=') + 1)), a
    ),
    {}
);

/**
 * @param {number[]} nums
 * @return {number[]}
 */
var productExceptSelf = function(nums) {
    var output = [];
    var leftMult = 1;
    var rightMult = 1;
    for (var i=nums.length - 1; i >= 0; i--) {
        output[i] = rightMult;
        rightMult *= nums[i];
        console.log({output: JSON.stringify(output), i})
    }
    for (var j=0; j < nums.length; j++) {
        output[j] *= leftMult;
        leftMult *= nums[j];
        console.log({output: JSON.stringify(output), j})
    }
    return output;
};

console.log(productExceptSelf([1, 2, 3, 4]))