20 Killer JavaScript One Liners ☝️

Hello Folks 👋

This is Savio here. I'm young dev with an intention to enhance as a successful web developer. I love building web apps with React. I have proved my superiority in frontend technologies.

Today, I'd like to share 20 Killer JavaScript one liners to make your life easier. Let's goooo 🚀

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Get Value of a brower Cookie

Retrieve the value of a cookie by accessing with document.cookie

const cookie = name => `; ${document.cookie}`.split(`; ${name}=`).pop().split(';').shift();

cookie('_ga');
// Result: "GA1.2.1929736587.1601974046"

Convert RGB to Hex

const rgbToHex = (r, g, b) =>
  "#" + ((1 << 24) + (r << 16) + (g << 8) + b).toString(16).slice(1);

rgbToHex(0, 51, 255); 
// Result: #0033ff

Copy to Clipboard

Easily copy any text to clipboard using navigator.clipboard.writeText.

const copyToClipboard = (text) => navigator.clipboard.writeText(text);

copyToClipboard("Hello World");

Check if Date is Valid

Use the following snippet to check if a given date is valid or not.

const isDateValid = (...val) => !Number.isNaN(new Date(...val).valueOf());

isDateValid("December 17, 1995 03:24:00");
// Result: true

Find the day of year

Find which is the day by a given date.

const dayOfYear = (date) =>
  Math.floor((date - new Date(date.getFullYear(), 0, 0)) / 1000 / 60 / 60 / 24);

dayOfYear(new Date());
// Result: 272

Capitalise a String

Javascript doesn't have an inbuilt capitalise function, so we can use the following code for the purpose.

const capitalize = str => str.charAt(0).toUpperCase() + str.slice(1)

capitalize("follow for more")
// Result: Follow for more

Find the number of days between two days

Find the days between 2 given days using the following snippet.

const dayDif = (date1, date2) => Math.ceil(Math.abs(date1.getTime() - date2.getTime()) / 86400000)

dayDif(new Date("2020-10-21"), new Date("2021-10-22"))
// Result: 366

Clear All Cookies

You can easily clear all cookies stored in a web page by accessing the cookie using document.cookie and clearing it.

const clearCookies = document.cookie.split(';').forEach(cookie => document.cookie = cookie.replace(/^ +/, '').replace(/=.*/, `=;expires=${new Date(0).toUTCString()};path=/`));

Generate Random Hex

You can generate random hex colors with Math.random and padEnd properties.

const randomHex = () => `#${Math.floor(Math.random() * 0xffffff).toString(16).padEnd(6, "0")}`;

console.log(randomHex());
// Result: #92b008

Remove Duplicated from Array

You can easily remove duplicates with Set in JavaScript. Its a life saver.

const removeDuplicates = (arr) => [...new Set(arr)];

console.log(removeDuplicates([1, 2, 3, 3, 4, 4, 5, 5, 6]));
// Result: [ 1, 2, 3, 4, 5, 6 ]

Get Query Params from URL

You can easily retrieve query params from a url either by passing window.location or the raw URL goole.com?search=easy&page=3

const getParameters = (URL) => {
  URL = JSON.parse('{"' + decodeURI(URL.split("?")[1]).replace(/"/g, '\\"').replace(/&/g, '","').replace(/=/g, '":"') +'"}');
  return JSON.stringify(URL);
};

getParameters(window.location)
// Result: { search : "easy", page : 3 }

Log Time from Date

We can log time, in the format hour::minutes::seconds from a given date.

const timeFromDate = date => date.toTimeString().slice(0, 8);

console.log(timeFromDate(new Date(2021, 0, 10, 17, 30, 0))); 
// Result: "17:30:00"

Check if a number is even or odd

const isEven = num => num % 2 === 0;

console.log(isEven(2)); 
// Result: True

Find Average of Numbers

Find the average between multiple numbers using reduce method.

const average = (...args) => args.reduce((a, b) => a + b) / args.length;

average(1, 2, 3, 4);
// Result: 2.5

Scroll to Top

You can use window.scrollTo(0, 0) method to automatic scroll to top. Set both x and y as 0.

const goToTop = () => window.scrollTo(0, 0);

goToTop();

Reverse a string

You can easily reverse a string using split, reverse and join methods.

const reverse = str => str.split('').reverse().join('');

reverse('hello world');     
// Result: 'dlrow olleh'

Check if array is empty

Simple one liner to check if an array is empty, will return true or false.

const isNotEmpty = arr => Array.isArray(arr) && arr.length > 0;

isNotEmpty([1, 2, 3]);
// Result: true

Get Selected Text

Get the text the user has select using inbuilt getSelection property.

const getSelectedText = () => window.getSelection().toString();

getSelectedText();

Shuffle an Array

Shuffling an array is super easy with sort and random methods.

const shuffleArray = (arr) => arr.sort(() => 0.5 - Math.random());

console.log(shuffleArray([1, 2, 3, 4]));
// Result: [ 1, 4, 3, 2 ]

Detect Dark Mode

Check if a user's device is in dark mode with the following code.

const isDarkMode = window.matchMedia && window.matchMedia('(prefers-color-scheme: dark)').matches

console.log(isDarkMode) // Result: True or False

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👀 Wrapping Up

Yeah, that's a wrap. Hope you enjoyed the article. Do not hesitate to share your feedback. I am on Twitter @saviomartin7. Give a follow!

Follow me on Github @saviomartin, Don't miss my amazing projects! 💯

Feedbacks are greatly appreciated! 🙌 Have an amazing day!

Savio Martin ⚡️

@saviomartin7

10 Killer JavaScript Snippets for Web Developers 🔥

One line JavaScript snippets to boost up your productivity. 98.8% people don't know all of them!

A thread 🧵👇️

07:06 AM - 20 Sep 2021

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Comments

[Alex Melvin]

Check if an array is not empty?
let arr = [];
arr?.some(x => x)

[Alex Melvin]

I'd do padStart instead of padEnd bacause of the obvious reasons.

const randomHex = () => #${Math.floor(Math.random() * 0xffffff).toString(16).padStart(6, "0")};

[Robson Muniz]

Nice content, Savio Martin, thanks for sharing it with us!

[Jose Granja Martinez]

Nice one! I wrote a similar article not long ago. Please check my take on the subject here

[Christian Diederich]

I like this one: await new Promise(r => setTimeout(r, 2000))

[Dumitru Uzun]

Shorter:

const isDateValid = (...val) => !Number.isNaN(+new Date(...val));
const dayDif = (date1, date2) => Math.ceil(Math.abs(date1 - date2) / 86400000);
const randomHex = () => `#${((1<<24)|Math.random() * 0xffffff).toString(16).slice(1)}`;

[jinbo.wang]

great

[Timothy Huang]

Thanks for sharing. Well done.

[Timur Murtukov]

Nah, these are not killer one-liners, just a beginner level. Besides that, writing something in 1 line doesn't mean good. It can sometimes harm readability, for example the first snippet is just a good example of how NOT to write your code.

And some of the examples are pretty useless. Why would you create a function for window.scrollTo(0, 0)? It's short enough on its own to use it directly.

In fact you just stolen all these snippets either from 30secondsofcode.org/ or from StackOverflow (I checked) and you have audacity to call yourself "superior". If you are really "an enthusiastic frontend developer" as you call yourself, than go and learn instead of posting useless articles.

[André Castelo]

He's 14 though, give him a break.

[Rahul]

hahah seriously?

go do a background research on him, 14 and oversmart and fooling on internet.

[Luis]

That's great. Just one correction: "capitalise"¹ is applied to each word in a string. In your example, it should be "upper case first" or something like that.

Best regards.

¹ developer.apple.com/documentation/...

[Erick Eduardo Petrucelli]

Since line breaks are optional in JavaScript, any code can be one line if you want to. 🤣

Ok, jokes aside, I understand one liner functions have appeal with developers, since Functional Programming is receiving full love nowadays.

So if anyone here needs to convert browser's rgb string to hex: stackoverflow.com/a/3627747/424498. This way you can directly send the result of a getComputedStyle(someElement).backgroundColor call to the one line function and receive the hex string as result.

[martin2844]

Good post. Just wanted to comment that making a set removes duplicates but also converts the array into a set. It stops being an array.

[Nacho Iacovino ⚡]

It's not a set because he's spreading it inside an array, so it becomes an array again.

[Lars Rye Jeppesen]

Removing duplicates example will not work for deep objects.

[0826gm]

Array shuffling this way won't be statistically random, it's biased due to how sort works with non-deterministic compare function. I propose changing the snippet to the similar

const shuffleArray = (arr) => arr.map(e => [Math.random(), e]).sort((a,b) => a[0] - b[0]).map(e => e[1]);

...which assigns a random "position" to each element, compares by those, then discards them.

There are even better ways (O(n)).

For more on this, see stackoverflow.com/q/2450954/8376184

[Matt Ellen]

This has come up before!

Frederik Ring • Aug 12

Nice post. Be aware that shuffling an Array like this is not perfectly random and a proper implementation is a little more complicated: medium.com/@nitinpatel_20236/how-t...