DEV Community

Jaxongir
Jaxongir

Posted on

21 Must Have JavaScript One Liners

Hi guys, in this post, I'm going to introduce JavaScript one liners that make you better JavaScript developer as they are very useful in most practical cases

1. Reverse a string

const reverseString = (str) => str.split("").reverse().join("");
console.log(reverseString("hello guys!"));
// !syug olleh
Enter fullscreen mode Exit fullscreen mode

2. Flatten an array

const flattenArray = (arr, flattenLevel = 1) => arr.flat(flattenLevel);
console.log(flattenArray([1, 2, [3, 4]]));
// [1,2,3,4]
console.log(flattenArray([1, 2, [3, 4, [5]]], 2));
// [1,2,3,4, 5]
Enter fullscreen mode Exit fullscreen mode

3. Shuffle an array

const shuffleArray = (arr) => arr.sort((a, b) => 0.5 - Math.random());
console.log(shuffleArray([1, 2, 3, 4, 5]));
// [2, 5, 4, 1, 3]
Enter fullscreen mode Exit fullscreen mode

4. Get a random boolean value

const getRandomBooleanValue = () => Math.random() >= 0.5;
console.log(getRandomBooleanValue());
// false
console.log(getRandomBooleanValue());
// true
Enter fullscreen mode Exit fullscreen mode

5. Find an average array value

const getAverageValue = (numbers) =>
  numbers.reduce((total, currEl) => total + currEl, 0) / numbers.length;
console.log(getAverageValue([1, 2, 3, 4]));
// 2.5
console.log(getAverageValue([100, 900]));
// 500
Enter fullscreen mode Exit fullscreen mode

6. Detect a dark mode

const darkMode = window.matchMedia && window.matchMedia('(prefers-color-scheme: dark)').matches;
Enter fullscreen mode Exit fullscreen mode

7. Scroll to the top of the page

const scrollToTop =() => window.scrollTo({top: 0, behavior: 'smooth'});
Enter fullscreen mode Exit fullscreen mode

8. Find number of specified character in a string

const getCharAmount = (string, char) => string.split(char).length - 1;
console.log(getCharAmount("hello", "l"));
// 2
console.log(getCharAmount("hello", "q"));
// 0
Enter fullscreen mode Exit fullscreen mode

9. Redirect URL

const redirectUrl = url => location.href = url;
redirectUrl("https://youtube.com");
Enter fullscreen mode Exit fullscreen mode

10. Detect whether an array is empty

const isArrayEmpty = (arr) => !Array.isArray(arr) || !arr.length;
console.log(isArrayEmpty([1, 2]));
// false
console.log(isArrayEmpty([]));
// true
Enter fullscreen mode Exit fullscreen mode

11. Return unique values from an array

const getUniqueArrayValues = (arr) =>
  arr.filter((i) => arr.indexOf(i) === arr.lastIndexOf(i));
console.log(getUniqueArrayValues([1, 2, 2, 3]));
// [1, 2, 3]
Enter fullscreen mode Exit fullscreen mode

12. Get a selected text from DOM

const getSelectedText = () => window.getSelection().toString();
Enter fullscreen mode Exit fullscreen mode

13. Check whether expression is an array

const isArray = (expression) => Array.isArray(expression);
console.log(isArray(1));
// false
console.log(isArray({ name: "Jaxongir" }));
// false
console.log(isArray(["JavaScript"]));
// false
Enter fullscreen mode Exit fullscreen mode

14. Check a number if it's odd or even

const isOdd = (number) => number % 2 === 1;
console.log(isOdd(1));
// true
console.log(isOdd(2));
// false
Enter fullscreen mode Exit fullscreen mode

15. Detect whether an element is in focus

const isElementFocussed = (element) => element === document.activeElement;
Enter fullscreen mode Exit fullscreen mode

16. Convert celsius to fahrenheit and vice versa

const convertCelsiusToFahrenheit = (celsius) =>
  Math.floor((celsius * 9) / 5 + 32);
const convertFahrenheitToCelsius = (fahrenheit) =>
  Math.floor((fahrenheit - 32) * (5 / 9));

console.log(convertCelsiusToFahrenheit(21));
// 69
console.log(convertCelsiusToFahrenheit(-50));
// -58

console.log(convertFahrenheitToCelsius(33));
// 0
console.log(convertFahrenheitToCelsius(22));
// -6
Enter fullscreen mode Exit fullscreen mode

17. Check if two arrays are the same

const isArraysTheSame = (arr1, arr2) =>
  arr1.length === arr2.length &&
  arr1.every((val, index) => val === arr2[index]);
console.log(isArraysTheSame([1, 2], [1, 2]));
// true
console.log(isArraysTheSame([1, 2], [1, 3]));
// false
Enter fullscreen mode Exit fullscreen mode

18. Convert first character to an uppercase

const convertFirstCharToUppercase = (str) =>
  `${str[0].toUpperCase()}${str.slice(1)}`;
console.log(convertFirstCharToUppercase("jaxongir"));
// Jaxongir
Enter fullscreen mode Exit fullscreen mode

19. Converting 24-hour clock to 12-hour clock

const convert24hTo12h = (hour) =>
  `${hour % 12 === 0 ? 12 : hour % 12}${hour > 23 || hour < 12 ? "am" : "pm"}`;
console.log(convert24hTo12h(1));
Enter fullscreen mode Exit fullscreen mode

20. Replace character of string with another character

const replaceStringCharacter = (str, char) => str.replace(/e/i, char);
console.log(replaceStringCharacter("geat", "re"));
// great
Enter fullscreen mode Exit fullscreen mode

21. Remove undefined or null from an array

const removeNullAndUndefined = (arr) =>
  arr.filter((val) => val != null || val != undefined);
console.log(removeNullAndUndefined([1, null, undefined, 4]));
// [1, 4]
Enter fullscreen mode Exit fullscreen mode

Top comments (0)