KevinVR

import React, {useState, useMemo} from 'react';

// Define an arrayValue prop
const UseMemoComponent = ({arrayValue}) => {

  // Create an object with the arrayValue prop
  const myArray = useMemo(() => {
    // If the value is undefined, default to 1
    const myValue = arrayValue || 1;
    

KevinVR

import React, {useState, useCallback} from 'react';

// Define an arrayValue prop
const UseCallbackComponent = ({arrayValue}) => {

  // Memoize callback with useCallback
  // Ensure the reference is always the same as long as the function doesn't change
  // So children components do not re-render due to a redundant variable reference change
  // Since functions are pass by reference
  const createArray = useCallback(() => {

KevinVR

import React, {useState, useMemo} from 'react';

// Import the useSelector hook from the react-redux package
import { useSelector } from 'react-redux'

const UseSelectorComponent = ({arrayValue}) => {
  // Retrieve myArray from the Redux store
  const myArray = useSelector(state => state.myArray);

  return <>

KevinVR

const moment = require('moment');

const databaseDate = '06/01/2021 9:59:01 PM GMT+2';
const jsDate = moment(databaseDate);

console.log(jsDate);
// > Tue Jun 01 2021 21:59:01 GMT+0200

// Calculate time difference from now
console.log(jsDate.fromNow());

KevinVR

const moment = require('moment');

const databaseDate = '06/01/2021 9:59:01 PM GMT+2';
var jsDate = moment(databaseDate, "DD/MM/YYYY HH:mm:ss");

console.log(jsDate);
// > Wed Jan 06 2021 09:59:01 GMT+0100 (CET)

// Calculate time difference from now
console.log(jsDate.fromNow());

KevinVR

new Date().getTime()
< 1614547103822

KevinVR

new Date(1614547103822)
// < Sun Feb 28 2021 22:18:23 GMT+0100 (CET)

KevinVR

import java.util.ArrayList;

// Let's develop our first solution
public class CountingDuplicates {
  public static int duplicateCount(String text) {
    // We need to count the amount of characters which have duplicates (not the amount of duplicates)
    int totalCharsWithDupes = 0;
    
    // Keep an array of characters which have already been counted towards the totalDupes counter
    // Since we want to count the amount of characters which have duplicates

KevinVR

import java.util.HashMap;
import java.util.Map;

public class CountingDuplicates {
  public static int duplicateCount(String text) {
    // Keep our a list with the number of duplicates per character
    // HashMap<Character, NumberOfDuplicates>
    HashMap<Character, Integer> hashMap = new HashMap<Character, Integer>();
    
    // Let's only loop once over the full input

KevinVR

<script>
	class MyButton extends HTMLElement {
		constructor() {
			super();
		}
	}
	customElements.define('my-button', MyButton);
</script>

<my-button></my-button>