DEV Community

Cover image for 20 Killer JavaScript One Liners ☝️
Savio Martin
Savio Martin

Posted on • Edited on

20 Killer JavaScript One Liners ☝️

#javascript #github #programming #productivity

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"
Enter fullscreen mode Exit fullscreen mode

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
Enter fullscreen mode Exit fullscreen mode

Copy to Clipboard

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

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

copyToClipboard("Hello World");
Enter fullscreen mode Exit fullscreen mode

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
Enter fullscreen mode Exit fullscreen mode

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
Enter fullscreen mode Exit fullscreen mode

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
Enter fullscreen mode Exit fullscreen mode

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
Enter fullscreen mode Exit fullscreen mode

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=/`));
Enter fullscreen mode Exit fullscreen mode

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
Enter fullscreen mode Exit fullscreen mode

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 ]
Enter fullscreen mode Exit fullscreen mode

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 }
Enter fullscreen mode Exit fullscreen mode

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"
Enter fullscreen mode Exit fullscreen mode

Check if a number is even or odd 

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

console.log(isEven(2)); 
// Result: True
Enter fullscreen mode Exit fullscreen mode

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
Enter fullscreen mode Exit fullscreen mode

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();
Enter fullscreen mode Exit fullscreen mode

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'
Enter fullscreen mode Exit fullscreen mode

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
Enter fullscreen mode Exit fullscreen mode

Get Selected Text

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

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

getSelectedText();
Enter fullscreen mode Exit fullscreen mode

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 ]
Enter fullscreen mode Exit fullscreen mode

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
Enter fullscreen mode Exit fullscreen mode

Do you want to test your project?

Try LambdaTest, test your browers in 3000+ browers like that with an image of your website
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 (43)

Collapse
 
jonrandy profile image
Jon Randy 🎖️ • • Edited 
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())
Enter fullscreen mode Exit fullscreen mode

😊

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

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

Collapse
 
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.

Thread Thread
 
webreflection profile image
Andrea Giammarchi • • Edited

P.S.

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

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

const reverse = str => [...str].reverse().join``;
Enter fullscreen mode Exit fullscreen mode
Collapse
 
jonrandy profile image
Jon Randy 🎖️ • • Edited

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

Collapse
 
silverium profile image
Soldeplata Saketos •

alternative reverse:

const reverse = str => [...str].reduceRight((a,v)=> a+v)
Enter fullscreen mode Exit fullscreen mode

:D

Collapse
 
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))
Collapse
 
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)

Collapse
 
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.

Collapse
 
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.

Collapse
 
lluismf profile image
Lluís Josep Martínez •

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

Collapse
 
silverium profile image
Soldeplata Saketos •

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

Thread Thread
 
codingjlu profile image
codingjlu •

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

Collapse
 
ashu profile image
Ashutosh Sharma •

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

Collapse
 
zeys profile image
zeys •

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

Collapse
 
andrecastelo profile image
André Castelo •

He's 14

Collapse
 
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.

Collapse
 
andrecastelo profile image
André Castelo •

He's 14 though, give him a break.

Collapse
 
rahxuls profile image
Rahul •

hahah seriously?

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

Collapse
 
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-...

Collapse
 
jonrandy profile image
Jon Randy 🎖️ • • Edited

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

Collapse
 
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.

Collapse
 
jonrandy profile image
Jon Randy 🎖️ • • Edited

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

Math.floor(Math.random() * x)
Enter fullscreen mode Exit fullscreen mode

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

Collapse
 
tracygjg profile image
Tracy Gilmore •

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

Collapse
 
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)}`;
Enter fullscreen mode Exit fullscreen mode
Collapse
 
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]);
Enter fullscreen mode Exit fullscreen mode

...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

Collapse
 
mellen profile image
Matt Ellen-Tsivintzeli • • Edited

This has come up before!

m90 profile image Frederik Ring •

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...

Collapse
 
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.

View full discussion (43 comments)

Some comments may only be visible to logged-in visitors. Sign in to view all comments.

Read next

ayoola_damilare_212d5bde0 profile image

My React Journey: Day 15

Ayoola Damilare -

velan profile image

Why EchoAPI is a Better Choice Than Postman for Your API Needs

Velan<> -

arjun98k profile image

Conditional Statements and Loops in JavaScript

arjun -

mdarifulhaque profile image

2779. Maximum Beauty of an Array After Applying Operation

MD ARIFUL HAQUE -