Advanced HTML + CSS

Git

• Repository

  • Local repository (files on disk)
    • contains .git folder
    • git clone https://github.com/zarybnicky/SDAPython-7.git => local clone of the repo
  • Remote repository (GitHub, GitLab)
    • Main Repo:
      • zarybnicky/SDAPython-7 = writable only by owner (zarybnicky)
    • Fork = copy of the main repo:
      • davidjopcik/SDAPython-7 = writable only by owner (davidjopcik)

• "Remote" (git remote -v) = reference to a remote repository by URL

  • "origin" - where was this repo cloned from
  • "upstream" - where was "origin" forked from

• git commit = creates a commit

• git status = prints out the state of the local repositorz

• git log --oneline --graph --all = prints out the commit graph

• git push upstream = upload local commits to a remote repo

• git fetch --all = download commits from a remote repo

• git pull --rebase [origin] = fetch + rebase

• git pull --rebase upstream = fetch + rebase

• "Pull Request" (PR)

  • = "git push" between remote repos
  • needs confirmation by owner or remote repo

• stash = temporary storage of uncommitted changes

  • git stash = save changes and hide them
  • git stash pop = apply saved changes
  • git stash && git pull --rebase upstream && git stash pop

CSS selectors

CSS combinators

/* Selector list, multiple elements
  <div class="p-1"></div> ...  <div class="p-2"></div>
*/
.p-1, .p-2 {}  

/* Descendant combinator, p-2 inside p-1
  <div class="p-1">
    <div>
      <div class="p-2"></div>
    </div>
  </div>    
  */
.p-1 .p-2 {} 

/* Child combinator, p-2 directly inside p-1
  <div class="p-1">
    <div class="p-2"></div>
  </div>
*/
.p-1 > .p-2 {}

/* General sibling combinator, p-2 somewhere after p-1
  <div>
    <div class="p-1"></div>
    <div></div>
    <div class="p-2"></div>
  </div>
*/
.p-1 ~ .p-2 { /* styling p-2 */ }

/* Adjacent sibling combinator, p-2 after p-1
  <div>
    <div class="p-1"></div>
    <div class="p-2"></div>
    <div></div>
  </div>
*/
.p-1 + .p-2 { /* styling p-2 */ }

CSS pseudo classes

• :hover - on mouse over

• :active - on mouse click, on TAB select

• :focus - has cursor, active (text) input alement

• :visited - link that has been visited

• :disabled - <button disabled>...</button>, input

• :invalid

  • input element with invalid value
  • <input type="number" pattern="\d+" required>

• :nth-of-type(odd)

  • Bootstrap class="table table-striped"
  • table.table-striped tr:nth-of-type(even) { ... }

• :first-child, :last-child

  • list of items with separators
  • ul > li { border-left: 1px solid black; }
  • ul > li:first-child { border-left: none; }

• :not( ... )

  • negation of the selector inside
  • .btn:not(.loading)

CSS pseudo elements

• ::before, ::after
• insert an element as the first/last child of an element
• content is controlled by CSS property content: ""
• content: none = ::after doesn't exist
• content: "" = ::after exists and is empty
• content: "..." = ::after exists and contains "..."
• also accepts background-image etc. for images

Search by attributes

/* <input  name="password"  /> */
.card input[name='password'] { }

/* <button type="submit"> ... </button> */
button[type="submit"] { }

CSS

BEM

Block, Element, Modifier = CSS naming convention

• .loading-button = Block
• .loading-button__text = Block + Element
• .loading-button--loading = Block + Modifier
• .loading-button__text--hidden = Block + Element + Modifier
• .loading-button__left__text--hidden = Block + Element + Modifier

Position

• static = default value, "natural placement"
• relative = "natural placement" + offset/padding
• absolute = "no natural placement" + top/left/... = coordinates relative to the parent element or to body

Float

• "Obtékání textu kolem obrázku"

• float: none/left/right

• Possible to use for layout, but NOT recommended

• requires the use of a "clearfix"

Sizing: vw, vh

vw = viewport width vh = viewport height

Media queries

@media (prefers-color-scheme: dark) {
    /*dark mode*/
}
@media (max-width: 480px) {
  .left-container, .right-container {
    width: 100%;
  }
}

box-shadow

/* box-shadow: blur-radius | spread-radius */
box-shadow: 10px 5px;
/* box-shadow: offset-x | offset-y | blur-radius | spread-radius | color */
box-shadow: 5px 10px 10px 5px red;

border-radius

/* small, fixed */
border-radius: 5px;

/* circle */
border-radius: 50%;

linear-gradient, radial-gradient

/* start-color, end-color */
background: linear-gradient(#e66465, #9198e5);
/* rotation, start-color, middle-color, end-color */
background: linear-gradient(45deg, blue, violet, red);

/* radial = circular */
background: radial-gradient(red 0, blue, green 100%)

object-fit

object-fit: cover; /* fill (default), contain */

Flexbox for vertical + horizontal centering

display: flex;
align-items: center;
justify-content: center;

transition

Transition = přechod/animace/prolnutí mezi dvěmi stavy

.transition {
    position: absolute;
    top: 0px;
    transition: 1s top;
}
.transition.done {
    top: -5px;
}
.transition:hover {
    top: 5px;
}

#example-element {
    transition: margin-right 2s;
    background-color: #e4f0f5;
    color: #000;
    margin-right: 0;
}
#example-element:hover {
    background-color: #909;
    color: #fff;
    margin-right: 40%;
}

animation

Delší sekvence CSS hodnot

#purple-button {
  animation: 3s purpleify;
}

@keyframes purpleify {
  from {
    background-color: #e4f0f5;
    color: #000;
  }
  to {
    background-color: #909;
    color: #fff;
  }
}

.bubble {
    position: absolute;
    top: 50px;
    right: 50px;
    animation: rotate 3s infinite;
}

@keyframes rotate {
    from {
        transform: rotate(0deg);
    }
    to {
        transform: rotate(360deg);
    }
}

transform

transform: rotate(0.5turn);

transform: scaleX(-1) rotate(0deg);

transform-origin: center;
transform-origin: top left;

JavaScript, DOM

Arrow function vs Function function

function addOne(i) {
    return i + 1;
}
const addOne = function (i) {
    return i + 1;
}
const addOne = (i) => {
    return i + 1;
};
const addOne = (i) => i + 1;

function eventHandler(event) {
    console.log(this);
}
const eventHandler = (event) => {
    console.log(this);
};

Finding a DOM element

const element = document.getElementById("id-without-hash");
const element = document.querySelector(".box > button");

Adding an event listener to an element

element.addEventListener("event-name", function (event) {
    console.log(this);
    console.log(event)
});

// (obsolete)
element.onclick = function () {};

Disabling a button, input, ...

element.disabled = true;
element.disabled = false;

//<button disabled> ... </button>

Working with CSS classes in JS

element.className = "class-one class-two";

element.classList.add("class")
element.classList.remove("class")
element.classList.toggle("class")

Change the text of a button

const originalText = element.innerText;
element.innerText = "Loading...";
// ...
element.innerText = originalText

Animation, delayed function call

// Single function execution
setTimeout(callback, 20); 
requestAnimationFrame(callback);

// Repeated function execution
let intervalId = setInterval(callback, 20);
clearInterval(intervalId)

• CSS animations (transition, animation):
  • simple to write/read, simple to debug
  • use only for simple animations
  • transition: on hover
  • animation: invalid form submission
• JS animation (requestAnimationFrame):
  • complex to use
  • possibly requires a library (https://greensock.com/gsap/)
  • usable for any animation - CSS, Canvas, WebGL, ...