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Savio Martin
Savio Martin

Posted on • Updated on

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 🚀


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"
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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
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Copy to Clipboard

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

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

copyToClipboard("Hello World");
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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
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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
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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
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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
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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=/`));
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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
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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 ]
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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 }
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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"
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Check if a number is even or odd

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

console.log(isEven(2)); 
// Result: True
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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
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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();
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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'
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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
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Get Selected Text

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

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

getSelectedText();
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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 ]
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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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Image description


👀 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!

🌎 Lets connect

Top comments (44)

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jonrandy profile image
Jon Randy • Edited on
const rgbToHex = (...rgb)=>'#'+rgb.reduce((a,v)=>a+(256|v).toString(16).slice(1),'')
const rgbToHex = (...rgb)=>'#'+rgb.reduce((a,v)=>a+v.toString(16).padStart(2,0),'')

const randomHex = (a='facedb')=>[...a].reduce(x=>x+(a+0x3d00b615)[~~(Math.random()*16)],'#')
const randomHex = (f='reduce')=>[...f][f](a=>a+(~~(Math.random()*16)).toString(16),'#')
const randomHex = ()=>'#'+(~~(Math.random()*(1<<24))|1<<25).toString(16).slice(1)
const randomHex = ()=>'#'+(~~(Math.random()*(1<<24))).toString(16).padStart(6,0)
const randomHex = ()=>'#'+(~~(Math.random()*8**8)).toString(16).padStart(6,0)
// Anyone got any shorter?


const reverse = str=>[...str].reduce((a,v)=>v+a)

const isEven = x=>~x&1

const capitalize = ([a,...b])=>a.toUpperCase()+b.join('')
const capitalize = a=>a.replace(/./,a=>a.toUpperCase())
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😊

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Sloan, the sloth mascot
Comment deleted
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lluismf profile image
Lluís Josep Martínez

But who has the need in the real world / real apps to reverse a string? Nobody.

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webreflection profile image
Andrea Giammarchi

Faster !== Correct ... his string reverse breaks with code points, while [...str] doesn't.

Try it: OP reverse breaks the emoji with reverse('some 💩'); while this reduce suggestion doesn't.

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webreflection profile image
Andrea Giammarchi • Edited on

P.S.

// this works fast and correct at the same time
const reverse = str => [...str].reverse().join('');
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eioluseyi profile image
Emmanuel Imolorhe

In a bid to be obnoxious 😏 you could have shortened your code further by 2 characters 🌚

const reverse = str => [...str].reverse().join``;
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jonrandy profile image
Jon Randy • Edited on

I made no claim to it being faster, but in this case the reduce method is almost twice as fast - jsbench.me/3tkttupth4/1 - at least on Chrome. On Firefox though, the situation is reversed. Different JS engines, different optimisations I guess

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silverium profile image
Soldeplata Saketos

alternative reverse:

const reverse = str => [...str].reduceRight((a,v)=> a+v)
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:D

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siddharthshyniben profile image
Siddharth

Nice list!

Some things I want to mention

  1. You forgot const (or let) in the first code block
  2. You can get URL Params easily in modern browsers like so: Object.fromEntries(new URLSearchParams(window.location.search))
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dacurse profile image
DaCurse

For 2, I think converting to an object is pointless, nothing wrong with the URLSearchParams object (which is basically a Map)

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siddharthshyniben profile image
Siddharth

But it's not an actual object (like arguments is not an actual array), so If you want to do some advanced object stuff you need to convert it to an object.

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lucascardim profile image
LucasCardim

What do you mean with "I have proved my superiority in frontend technologies.". Be humble, you're not superior than anyone.

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ashu profile image
Ashutosh Sharma

I believe English is not his primary language(not mine either). I guess he means skill/competency.

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lluismf profile image
Lluís Josep Martínez

He has proved that he can copy paste from StackOverflow :-)

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silverium profile image
Soldeplata Saketos

but to distinguish the better code to copy is the hardest thing

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codingjlu profile image
codingjlu

Yes, especially when one post has 1k votes and another has -16?

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zeys profile image
zeys

Dont be hard on him he's just a kid (he's 14)

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andrecastelo profile image
André Castelo

He's 14

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jonrandy profile image
Jon Randy • Edited on

I think there is also an issue with your randomHex function - it will never return #ffffff since:

Math.floor(Math.random() * x)
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can only ever return values from 0 to x-1. You need to use Math.round()

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tracygjg profile image
TGJ Gilmore

Suggested alternative:
const capitalize = ([init, ...rest]) => init.toUpperCase() + rest.join('')

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murtukov profile image
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.

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andrecastelo profile image
André Castelo

He's 14 though, give him a break.

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manoharreddyporeddy profile image
Manohar Reddy Poreddy

Once I used to use JS to capitalize, and everything else.
Feedback comments came in from Experts
Now I just use the simpler CSS.
Ex: w3schools.com/cssref/pr_text_text-...

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jonrandy profile image
Jon Randy • Edited on

That doesn't do the same thing, merely changes the appearance of the string on screen - doesn't change the string. Depending on the use case, that could be okay

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manoharreddyporeddy profile image
Manohar Reddy Poreddy

Yes, but that was an example (Ex:) for conversation.
I used to do everything in JS
including building accessible menus, etc
wrote several 100s of lines of code for each.
In CSS, it was always less than 50 each, very easy to change, and by everyone.

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0826gm profile image
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]);
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...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

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mellen profile image
Matt Ellen • Edited on

This has come up before!

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...

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duzun profile image
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)}`;

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erickpetru profile image
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.

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casperbraske profile image
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/...

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alexmelw profile image
Alex Melvin

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

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alexmelw profile image
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")};

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chrdiede profile image
Christian Diederich

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

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che3vinci profile image
jinbo.wang

great

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