munkacsitomi

// Sorting with Array.prototype.filter()
const startWith0 = (arr) => [...arr.filter(x => x === 0), ...arr.filter(x => x !== 0)];
// Sorting with Array.prototype.sort()
// const startWith0 = (arr) => arr.sort((x) => x === 0 ? -1 : 1);

console.time('time');
console.log('result', startWith0([1, null, 'e', 0, 2, 'a', 123, undefined, false, 0, true, 'd', 0, true]));
console.timeEnd('time');

munkacsitomi

// this is wrong
for (var i = 0; i < 5; i++) {
  setTimeout(() => console.log(i), 1000); // => 5 5 5 5 5
}

// easy fix to use let instead of var. block level scoping instead of function level
for (let i = 0; i < 5; i++) {
  setTimeout(() => console.log(i), 1000); // => 0 1 2 3 4
}

munkacsitomi

const pause = (data, time) => new Promise(resolve => setTimeout(() => resolve(data), time));

const sequentialParallel = async () => {
  console.time('time');

  // Sequential
  // const first = await pause('first', 3000);
  // const second = await pause('second', 2000);

  // Parallel

munkacsitomi

const numbers = [1, 2, 3, 4, 12, 50];
const reducer = (accumulator, currentValue) => accumulator + currentValue;
const reducedNumbers = numbers.reduce((accumulator, currentValue) => accumulator + currentValue);
const multipliedNumbers = numbers.map(x => x * 2);

console.log(numbers.reduce(reducer)); // => 72
console.log(reducedNumbers); // => 72
console.log(multipliedNumbers); // => [ 2, 4, 6, 8, 24, 100 ]

munkacsitomi

// How to add and retrieve values in js with ES5
const counterES5 = () => {
  let storedNumber = 0;

  return {
    add: function(newNumber) {
      storedNumber += newNumber;
    },
    retrieve: function() {
      return storedNumber;

munkacsitomi

// Higher-Order Functions with ES5
function createBaseES5(x) {
  return function (y) {
    return x + y;
  }
}

const addTwo = createBaseES5(2);
console.log(addTwo(12)); // => 14
console.log(addTwo(23)); // => 25

munkacsitomi

// Not recommended - too sequential
async function logInOrder(urls) {
  for (const url of urls) {
    const response = await fetch(url);
    console.log(await response.text());
  }
}

// Recommended - nice and parallel
async function logInOrder(urls) {

munkacsitomi

// Copying an array
let copy = [...arr]

// Creating an array of unique elements
let uniqueElements = [...new Set(arr)]; 
let elementsStartingWithA = [...new Set(arr)].filter(e => e.startsWith('a')); 

// Concatenate arrays
let concat = [...arr1, ...arr2]; 

munkacsitomi

const fetchAndUpdatePosts = () => {
  fetchPosts()
    .then((posts) => {
      updatePosts(posts)
        .catch((err) => {
          console.log('error in updating posts');
        });
    })
    .catch(() => {
      console.log('error in fetching posts');

munkacsitomi

@keyframes listItemFadeIn {
  0% {
    opacity: 0;
  }
  100% {
    opacity: 1;
    margin-top: 0px;
  }
}