Video Player, Konami Code, and Local Storage

Custom HTML5 Video

  • double underscore in CSS and HTML is a sub-element that is modified
  • video properties (currentTime, paused, textContent, offsetX)
  • more addEventListener use!

Key Sequence Detection

const pressed = [];
const secretCode = 'wesbos';
window.addEventListener('keyup', (e) => {
  pressed.splice(-secretCode.length - 1, pressed.length - secretCode.length);
  if (pressed.join('').includes(secretCode)) {
    console.log('DING DING!');
  • konami code (like Easter eggs)
  • cornify all the things! (unicorns and rainbows everywhere)

Slide in on Scroll

  • debounce = limiting the rate at which events fire in order to improve performance
  • copying code snippets like debounce are the way of the dev rather than reinventing the wheel
  • a bit of event listening and math process involved in order for this to function
  • I’m definitely leaning toward arrow functions as a preference which make methods like forEach() easier to comprehend

Object and Arrays – Reference vs Copy

  • Booleans, strings, and number variable reference to a variable will not change when the original is changed
  • Reference of an array references back to original array, so change happens within the original array
  • To make an actual copy rather than a reference:
    • array.slice()
    • [].concat(array)
    • […array]
  • objects work the same way in referencing as an array
  • To copy an object:
    • Object.assign({}, person, {number:99}) //only one level deep
    • {…person} //React
// start with strings, numbers and booleans
    // let age = 100;
    // let age2 = age;
    // console.log(age, age2);
    // age = 200;
    // console.log(age, age2);

    // let name = 'Wes';
    // let name2 = name;
    // console.log(name, name2);
    // name = 'wesley';
    // console.log(name, name2);

    // Let's say we have an array
    const players = ['Wes', 'Sarah', 'Ryan', 'Poppy'];

    // and we want to make a copy of it.
    const team = players;

    console.log(players, team);
    // You might think we can just do something like this:
    // team[3] = 'Lux';

    // however what happens when we update that array?

    // now here is the problem!

    // oh no - we have edited the original array too!

    // Why? It's because that is an array reference, not an array copy. They both point to the same array!

    // So, how do we fix this? We take a copy instead!
    const team2 = players.slice();

    // one day

    // or create a new array and concat the old one in
    const team3 = [].concat(players);

    // or use the new ES6 Spread
    const team4 = [...players];
    team4[3] = 'heeee hawww';

    const team5 = Array.from(players);

    // now when we update it, the original one isn't changed

    // The same thing goes for objects, let's say we have a person object

    // with Objects
    const person = {
      name: 'Wes Bos',
      age: 80

    // and think we make a copy:
    // const captain = person;
    // captain.number = 99;

    // how do we take a copy instead?
    const cap2 = Object.assign({}, person, { number: 99, age: 12 });

    // We will hopefully soon see the object ...spread
    // const cap3 = {...person};

    // Things to note - this is only 1 level deep - both for Arrays and Objects. lodash has a cloneDeep method, but you should think twice before using it.

    const wes = {
      name: 'Wes',
      age: 100,
      social: {
        twitter: '@wesbos',
        facebook: 'wesbos.developer'


    const dev = Object.assign({}, wes);

    const dev2 = JSON.parse(JSON.stringify(wes));

Local Storage and Event Delegation

  • a little SVG exposure
  • submit event listener is best for when is button is clicked (or someone hits Enter key)
  • .preventDefault() prevents page from reloading
  • CSS trick for hiding checkbox to insert custom checked image
  • ES6 makes innerHTML much easier to work with!
  • learned about localStorage to keep list items even after refresh
  • event delegation targets parent so it can relay event listeners to children

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