7 Killer JavaScript One-Liners that you must know

1. Generate Random String
if you will ever need a temporary unique id for something. this
one-liner will generate a random string for you

const randomString = Math.random().toString(36).slice(2);
console.log(randomString); //output- r0zf1xfqcr (the string will be random )

2. Extract Domain Name From An Email
you can use the substring() method to extract the domain name
of the email.

let email = '[e-mail]';
le getDomain = email.substring(email.indexOf('@') + 1);

console.log(getDomain); // output - gmail.com

3. Detect Dark Mode
with this one-liner, you can check if the user is using dark mode ( and then you can update some functionality according to dark mode)

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

4. Check if An Element is Focused
to detect if the element has the focus in JavaScript, you can use the read-only property activeElement of the Document object.

const elem = document.querySelector(' .text-input');

const isFocus = elem == document.activeElemnt;

/* isFocus will be true if elem will have focus, and isFocus will be false if elem will not have focus */

5. Check If An Array Is Empty
this one-liner will let you know if an array is empty or not.

let arr1 = [];
let arr2 = [2, 4, 6, 8, 10];

const arr1IsEmpty = !(Array.isArray(arr1) && arr1.length >0);
const arr2IsEmpty = !(Array.isArray(arr2) && arr2.length >0);

console.log(arr1); //output - true
console.log(arr2); // output - false

6. Redirecting User
you can redirect the user to any specific URL using JavaScript.

const redirect = url => location.href = url

/* call redirect (url) whenever you want to redirect the user to a specific url */

7. Check If A Variable Is An Array
You can check if any Variable is an Array or not using the Array.isArray() method.

let fruit = 'apple';
let fruits = ["apple", "banana", "mango", "orange", "grapes"];

const isArray = (arr) => Array.isArray(arr);

console.log(isArray.(fruit)); //output - false
console.log(isArray.(fruits)), //output- true

Comments

[m0nm]

Nice tips, but i think you made a mistake on the fifth tip. It should be like this:

console.log(arr1IsEmpty); //output - true
console.log(arr2IsEmpty); // output - false

[Pierre-Henry Soria ✨]

Thanks for sharing this Jamran 😊

[Basharath]

Hey, while inserting the code blocks, indicate the language so that it would be nicely highlighted.

```js -> this line

[Athif binu]

Thanks for share at that valuable information.

[Arnav Kumar]

Nice but there are some errors

like in tip 7
there should not be . after the isArray and there shouldn't be a , at the end it should be ;

fixed code

let fruit = 'apple';
let fruits = ["apple", "banana", "mango", "orange", "grapes"];

const isArray = (arr) => Array.isArray(arr);

console.log(isArray(fruit)); //output - false
console.log(isArray(fruits)); //output- true

[Bernd Wechner]

Poe's Law (look it up if you need to it's an essential part of modern internet vocabulary)

As in surely, when I read this, I read it as a parody, a joke ...

Replacing this:

console.log(Array.isArray(fruit)); //output - false

with this:

console.log(isArray(fruit)); //output - false

is a killer one-liner indeed. Well the killer one-liner is in fact:

const isArray = (arr) => Array.isArray(arr);

As in, it's one line, no-one needs (a killer).

And on a close inspection the errors aside (a hasty post it seems) they all seem to be in jest.

[Kosta Goncharov]

Sweet! The random string trick is super cool!

[Martin Krause]

Hey Kamran,

nice tricks! If you are interested in "one line functions", check out my series "awesome JavaScript in one line of code".

Cheers!

[Ajeetesh1999]

This was very helpful, thank you soo much for these useful tips.

[Kamran Ahmad]

always welcome

[alexkarpen]

(array1 || []).length

[IroncladDev]

Very nice tips! I really enjoy javascript one-liners and how useful and effective they are!

I believe to get the url of an email, an easier way is const emailUrl = email => email.split("@")[1]