Posted on Aug 7, 2020 • Edited on Aug 8, 2020

Creating a Bouncing Logo with JavaScript ⛹🏽‍♀️

So, recently I've seen a YouTube video about DVD bouncing logo and thought, why not create one using JavaScript and write a small tutorial about it? 🤔

And here's the result:

Recipe

First of all, let's deal with our HTML. We're not gonna go with a <canvas> today (sorry) but we have an awesome CodePen logo, so why not using it?

<svg xmlns="http://www.w3.org/2000/svg" id="label" viewBox="0 0 138 26" fill="none" stroke="#26de81" stroke-width="2.3" stroke-linecap="round" stroke-linejoin="round"> <path d="M80 6h-9v14h9 M114 6h-9 v14h9 M111 13h-6 M77 13h-6 M122 20V6l11 14V6 M22 16.7L33 24l11-7.3V9.3L33 2L22 9.3V16.7z M44 16.7L33 9.3l-11 7.4 M22 9.3l11 7.3 l11-7.3 M33 2v7.3 M33 16.7V24 M88 14h6c2.2 0 4-1.8 4-4s-1.8-4-4-4h-6v14 M15 8c-1.3-1.3-3-2-5-2c-4 0-7 3-7 7s3 7 7 7 c2 0 3.7-0.8 5-2 M64 13c0 4-3 7-7 7h-5V6h5C61 6 64 9 64 13z"/> </svg>

And that's it for HTML! This SVG image is the only thing we're going to operate with.

CSS

Now we spice it up a little bit by using CSS:

body { width: 100vw; height: 100vh; background-color: #0f0f13; overflow: hidden; position: relative; } #label { position: absolute; left: calc(50vw - 150px); top: calc(50vh - 28px); width: 300px; height: 56px; }

So now, that we have finally completed the warmup, we're ready for the hardest part!

JavaScript

Let's start by defining variables:

const body = document.querySelector('body') const label = document.querySelector('#label') let colors = [ '#26de81', '#fc5c65', '#fd9644', '#fed330', '#2bcbba', '#45aaf2', '#4b7bec', '#a55eea', '#ffc1f3', '#76ead7', '#ff9c71', '#32e0c4', '#d291bc', '#fa744f' ] let FPS = 60 let width , height , velocityX = 1 , velocityY = 1 , pause = true , previousColor = 0 ;

Velocity is needed for the bounce movement:

The absolute number defines the speed (minimum is 1)
The sign defines the direction
- For X-axis - positive number moves the logo right, negative - left
- For Y-axis - positive number moves the logo down, negative - up

For storing our window size we use width and height.

Now we need a function that will keep our width & height variables up to date and pause the animation if the window is smaller than an image.

const reset = () => { width = window.innerWidth || document.documentElement.clientWidth || document.body.clientWidth; height = window.innerHeight || document.documentElement.clientHeight || document.body.clientHeight; pause = width <= label.getBoundingClientRect().width || height <= label.getBoundingClientRect().height; label.style.left = 'calc(50vw - 150px)' label.style.top = 'calc(50vh - 28px)' label.style.stroke = colors[0] } reset()

It needs to be fired on initialization and each time window size changes, so let's create an event listener:

window.addEventListener('resize', reset, true)

Have you seen how the CodePen logo is changing colors? There is a separate function for doing that.

const getRandomColor = () => { let currentColor = -1 do { currentColor = Math.floor(Math.random() * colors.length); } while (previousColor == currentColor); previousColor = currentColor return colors[currentColor] }

Ok, it's time for the main function that will make our image bounce. For that purpose let's create an interval function:

setInterval(() => { if (pause) return; let rect = label.getBoundingClientRect() let left = rect.x let top = rect.y if (left + rect.width >= width || left <= 0) { velocityX = -velocityX let randomColor = getRandomColor() label.style.stroke = randomColor if (left + 150 <= width / 2) { body.style.boxShadow = `inset 4px 0px 0px 0px ${randomColor}` } else { body.style.boxShadow = `inset -4px 0px 0px 0px ${randomColor}` } } if (top + rect.height >= height || top <= 0) { velocityY = -velocityY let randomColor = getRandomColor() label.style.stroke = randomColor if (top + 28 <= height / 2) { body.style.boxShadow = `inset 0px 4px 0px 0px ${randomColor}` } else { body.style.boxShadow = `inset 0px -4px 0px 0px ${randomColor}` } } label.style.left = rect.x + velocityX + 'px' label.style.top = rect.y + velocityY + 'px' }, 1000 / FPS)

Ta-da 🎉! We have just created Bouncing Logo Screensaver!

But, let's take a closer look at the collision detection.

if (left + rect.width >= width || left <= 0) {

The condition above gives true if:

the position of the right side of the logo (left + rect.width) is greater or equal than the position of the right side of the window (width) on the X-axis
the position of the left side of the logo (left) is less or equal than the position of the left side of the window (0) on the X-axis

So, if the condition fires true, the following things happen:

The direction of the movement is being inverted: velocityX = -velocityX
Color Randomizer chooses a random color, saves it to the variable and updates image color
If-statement determines which side of the window is closer to the central coordinate of the logo and, depending on this, creates an inset box-shadow for one of the sides

Vertical collisions are being processed the same way.

So, I hope you enjoyed this article. Feel free to check me on: