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Short tricks of HTML, CSS and JavaScript II

Read Time:6 Minute, 13 Second

This article was originally published on medium.com

A modern list of HTML, CSS and JavaScript How Tos for everyday use. Feel free to comment your own approaches 🙂

This is the second part, if you missed the previous one: Short tricks of HTML, CSS and JavaScript

Access last element in Array

JS

[1, 2, 3].at(-1)
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It would be really nice to have [1, 2, 3][-1]

Horizontal and vertical center

The easiest way to center anything.
CSS

body { position: absolute; inset: 0; display: grid; place-items: center;
}
div { background-color: grey; width: 100px; height: 100px;
}
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View on JSFiddle here.

Date to local ISO string

JS

new Date().toLocaleString('sv')
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Sweden hack.

Lazy loading images and iframes

Defer loading of images/iframes that are off-screen until the user scrolls near them.
HTML

<img src="image.webp" loading="lazy">
<iframe src="game.html" loading="lazy"></iframe>
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Get string after last specific character

JS

'filename.pdf'.split('.').pop()
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HTML range value

Shortest version without form, min or external JavaScript.
HTML

<input type="range" value="0" max="10" oninput="num.value = this.value">
<output id="num">0</output>
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View on JSFiddle here.

Copy to clipboard

JS

navigator.clipboard.writeText('Mr Robot')
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Reset all CSS

CSS

* { all: unset;
}
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You can use it with any selector.

Get month name

JS

const today = new Date()
today.toLocaleString('default', { month: 'long' })
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You can set any language you want instead of browser’s default language.

Embedding PDF files into HTML

HTML

<object type="application/pdf" data="https://your_file.pdf"> <iframe src="https://docs.google.com/gview?embedded=true&url=https://your_file.pdf"/>
</object>
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Use object with iframe fallback to support all mobile browsers.
View on JSFiddle here.

Flip an image

CSS

img { transform: scaleX(-1); /* flip horizontally */
}
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Use scaleY(-1) to flip vertically.

Shuffle an array

JS

array.sort(() => 0.5 - Math.random())
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Select images with not alt attribute

CSS

img:not([alt]) { border: 2px solid red;
}
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Detect dark mode

JS

window.matchMedia('(prefers-color-scheme: dark)').matches
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Accept only specific files in an input

HTML

<input type="file" accept="image/*"> <!-- only images -->
<input type="file" accept=".pdf, .odt"> <!-- only pdf and odt -->
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Deep cloning an object

Assuming you don’t have functions inside you can use JSON methods.
JS

JSON.parse(JSON.stringify(object))
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Progress bar

You already have a native component for that.
HTML

<progress value=".7">Progress</progress>
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Smooth scroll behavior

CSS

html { scroll-behavior: smooth;
}
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Detect if your file is an image

JS

file.type.includes('image')
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Automatic email validation

Just place your email input inside a form.
HTML

<form> <input type="email" placeholder="[email protected]">
</form>
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View on JSFiddle here.

Transform image to WEBP format

Easier than you think using HTML5 canvas, blob and file rename trick to run it back into a file.
JS

function transform_to_WEBP(file) { return new Promise((resolve, reject) => { const image = new Image() image.onload = () => { const canvas = document.createElement('canvas') canvas.width = image.naturalWidth canvas.height = image.naturalHeight canvas.getContext('2d').drawImage(image, 0, 0) canvas.toBlob(blob => resolve(new File([blob], 'filename.webp')) , 'image/webp') } image.src = URL.createObjectURL(file) }) 
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We use a promise because loading the file takes time.

Lazy rendering anything

content-visibility is a CSS property that controls whether and when an element’s content is rendered. It only renders the content of an off-screen component when it becomes on-screen.
CSS

.element { content-visibility: hidden;
}
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Clear all cookies

JS

document.cookie.split(';').forEach(cookie => document.cookie = cookie.replace(/^ +/, '').replace(/=.*/, `=;expires=${new Date(0).toUTCString()};path=/`))
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Don’t show Material Icon text when loading font

We need to change @font-face declaration on the server and luckily we can use an API for modifying the font-display.
CSS

<link rel="stylesheet" href="https://fonts.googleapis.com/icon?family=Material+Icons&display=block">
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Get CSS Variable in JS

JS

getComputedStyle(document.documentElement) .getPropertyValue('--my-variable-name')
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Debug an Android PWA

  1. Allow USB debugging in your device and open your PWA.
  2. Install Android Debug Tools and check for devices.
  3. Open Chrome (Chromium) and go to chrome://inspect/#devices

Bash

sudo apt install android-tools-adb android-tools-fastboot
adb devices
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Analyse performance of pieces of your code

JS

console.time()
// your code
console.timeEnd()
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Capitalize first letter

JS

str.charAt(0).toUpperCase() + str.slice(1)
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Number of days between 2 days

JS

(date1, date2) => Math.ceil(Math.abs(date1.getTime() - date2.getTime()) / 86400000)
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Basic fade-in animation

Workaround to avoid display: none problems.
CSS

h1 { animation: fade 1s ease-in 3s forwards; pointer-events: none; opacity: 0;
}
@keyframes fade { 0% { opacity: 0; } 100% { opacity: 1; }
}
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View on JSFiddle here.

Get selected text

JS

window.getSelection().toString()
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Allow user to resize any element

CSS

div { overflow: auto; resize: both;
}
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View on JSFiddle here.

Check valid date

JS

(new Date(date) != 'Invalid Date') && !isNaN(new Date(date))
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HTML and CSS only interactive carousel

Snapping, clickable and responsive images in a carousel effect without JavaScript.
HTML

<g-carousel> <g-images> <a href="#b"><img id="a" src="https://source.unsplash.com/random/800x400?sig=1"></a> <a href="#c"><img id="b" src="https://source.unsplash.com/random/800x400?sig=2"></a> <a href="#a"><img id="c" src="https://source.unsplash.com/random/800x400?sig=3"></a> </g-images>
</g-carousel>
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CSS

g-carousel { display: block; width: 100%; overflow-x: scroll; scroll-snap-type: x mandatory; scroll-behavior: smooth;
}
a { display: contents;
}
g-images { display: flex; width: calc(100% * 3);
}
img { width: 100%; scroll-snap-align: center;
}
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View on JSFiddle here.


★ Do you love HTML, CSS and JavaScript as I do? ^^ Don’t forget to check my geek clothing about web development ;P

Source: https://dev.to/gengns/short-tricks-of-html-css-and-javascript-ii-4hpm

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