10 JavaScript One-Liner Code You Should Know

1. Deep clone object

This one-Liner will make a Deep clone of a javascript object:

const originalObject = {
  "studentId": 26334,
  "studentName":"John Doe",
  "totalMarks": 348.50
};

const clonedObject = structuredClone(originalObject);

console.log("Student details: ", clonedObject);

// Output: { studentId: 26334, studentName: "John Doe", totalMarks: 348.5 }

2. Truncate a String To a Specific Length

This is One-Liner is to truncate a string and add "..." to an end on a specific given length

const originalString = "The quick brown fox jumps over the lazy dog";

const truncate = (str, len) => str?.length > len ? str.slice(0, len) + "..." : str;

console.log("Truncated string: ", truncate(originalString, 9));

// Output: The quick...

3. Remove duplicate elements in array

This one-Liner will return a new array without duplicate elements from original array

const originalArray = [9,'a',8,'a','b',9,5,3,9,3.5,'b'];

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

console.log("Array without duplicates: ", removeDuplicates(originalArray));

 // Output: [ 9, "a", 8, "b", 5, 3, 3.5 ]

3. Swap numbers

This one liner swaps 2 numbers:

let a=6, b=9;

[a,b] = [b,a]

console.log(`Swapped Values - a: ${a} b: ${b}`);

// Output: Swapped Values - a: 9 b: 6

4. Flatten a nested array

This one liner helps you to flatten a nested array

const flattenArray = (arr) => [].concat(...arr);
console.log("Flattened: ", flattenArray([1, [2, 5, 6], 7,6, [2,3]])

// Output: Flattened: [ 1, 2, 5, 6, 7, 6, 2, 3 ]

5. Scroll To Top

This one liner instantly navigates you to the top of the page:

window.scrollTo(0, 0)

6. Find the Last Occurrence in an Array:

This one liner returns last occurrence of element in an array:

const lastIndexOf = (arr, item) => arr.lastIndexOf(item);
console.log("Last index of 7 is: ", lastIndexOf([7, 5, 6 , 7 , 3 , 4], 7))

// Output: Last index of 7 is:  3

7. Make Your Code Wait for a Specific Time

Sometimes we want to make our code wait out for a seconds,

const waitForIt = ms => new Promise(resolve => setTimeout(resolve, ms));
(async () => {
  console.log("Before waiting");
  await waitForIt(5000);
  console.log("After waiting for 5 seconds");
})();

/* Output: 
Before waiting
Promise { <state>: "pending" }
After waiting for 5 seconds   
*/

8. Extract a Property from an Array of Objects

Need to grab a specific property from an array of objects? Cherry-pick it!

const getValuesOfAKey = (arr, key) => arr.map(obj => obj[key]);
console.log("Values of a: ", getValuesOfAKey([{a: 1}, {a: 2}], 'a'));

// Output: Values of a: Array [ 1, 2 ]

9. Generate a Random Hexadecimal Color Code:

Get a random hex color code!

const randomColor = "#" + (~~(Math.random() * 8**8)).toString(16).padStart(6,0);
console.log("Generated code: ", randomColor);

// Output: Generated code:  #0cf199

10. Remove falsy values from array

const removeFalsy = (arr) => arr.filter(Boolean);
// or as suggested by Jon Randy
const removeFalsy = arr => arr.filter(x=>x)

console.log("Without falsy:", removeFalsy([true, false, undefined, NaN, null, false, true]))

// Output: Without falsy: [ true, true ]