28 JavaScript One-Liners Every Senior Developer Needs to Know

1. Swapping Values Without a Temporary Variable

   let a = 1, b = 2;
   [a, b] = [b, a];
   // Output: a = 2, b = 1

2. Object Destructuring for Easier Data Access

   const { name, age } = { name: 'John', age: 30 };
   // Output: name = 'John', age = 30

3. Cloning Objects in a Snap

   const originalObj = { name: 'Jane', age: 22 };
   const clonedObj = { ...originalObj };
   // Output: clonedObj = { name: 'Jane', age: 22 }

4. Merging Objects Made Simple

   const obj1 = { name: 'Jane' };
   const obj2 = { age: 22 };
   const mergedObj = { ...obj1, ...obj2 };
   // Output: mergedObj = { name: 'Jane', age: 22 }

5. Cleaning Up Arrays

   const arr = [0, 1, false, 2, '', 3];
   const cleanedArray = arr.filter(Boolean);
   // Output: cleanedArray = [1, 2, 3]

6. Transforming NodeList to Array

   const nodesArray = [...document.querySelectorAll('div')];

7. Checking Arrays for Specific Conditions

   const arr = [1, 2, 3, -1, 4];
   const hasNegativeNumbers = arr.some(num => num < 0);
   // Output: hasNegativeNumbers = true

   const allPositive = arr.every(num => num > 0);
   // Output: allPositive = false

8. Copying Text to Clipboard

   navigator.clipboard.writeText('Text to copy');

9. Creating a Unique Array

   const arr = [1, 2, 2, 3, 4, 4, 5];
   const unique = [...new Set(arr)];
   // Output: unique = [1, 2, 3, 4, 5]

10. Finding the Intersection of Two Arrays

    const arr1 = [1, 2, 3, 4];
    const arr2 = [2, 4, 6, 8];
    const intersection = arr1.filter(value => arr2.includes(value));
    // Output: intersection = [2, 4]

11. Sum of Array Values

    const arr = [1, 2, 3, 4];
    const sum = arr.reduce((total, value) => total + value, 0);
    // Output: sum = 10

12. Conditional Object Property

    const condition = true;
    const value = 'Hello World';
    const newObject = { ...(condition && { key: value }) };
    // Output: newObject = { key: 'Hello World' }

13. Dynamic Object Key

    const dynamicKey = 'name';
    const value = 'John Doe';
    const obj = { [dynamicKey]: value };
    // Output: obj = { name: 'John Doe' }

14. Online Status Checker

    const isOnline = navigator.onLine ? 'Online' : 'Offline';
    // Output: isOnline = 'Online' or 'Offline'

15. Confirm Before Page Leave

    window.onbeforeunload = () => 'Are you sure you want to leave?';

16. Sum of Object Values by Key

    const arrayOfObjects = [{ x: 1 }, { x: 2 }, { x: 3 }];
    const sumBy = (arr, key) => arr.reduce((acc, obj) => acc + obj[key], 0);
    sumBy(arrayOfObjects, 'x');
    // Output: 6

17. Parse Query String to Object

    const query = 'name=John&age=30';
    const parseQuery = query => Object.fromEntries(new URLSearchParams(query));
    // Output: parseQuery = { name: 'John', age: '30' }

18. Convert Seconds to Time String

    const seconds = 3661;
    const toTimeString = seconds => new Date(seconds * 1000).toISOString().substr(11, 8);
    toTimeString(seconds);
    // Output: '01:01:01'

19. Maximum Value in Object

    const scores = { math: 95, science: 99, english: 88 };
    const maxObjectValue = obj => Math.max(...Object.values(obj));
    maxObjectValue(scores);
    // Output: 99

20. Check if Object Contains Value

    const person = { name: 'John', age: 30 };
    const hasValue = (obj, value) => Object.values(obj).includes(value);
    hasValue(person, 30);
    // Output: true

21. Boosting Scores Conditionally

    const scores = [45, 75, 62, 55, 90];
    const updatedScores = scores.map(score => score < 60 ? score + 20 : score);
    // Output: updatedScores = [65, 75, 62, 75, 90]

22. Safely Accessing Nested Object Properties

    const user = { profile: { name: 'John Doe' } };
    const userName = user.profile?.name ?? 'Anonymous';
    // Output: userName = 'John Doe'

23. Conditional Execution

    const isEligible = true;
    isEligible && performAction();
    // performAction is called if isEligible is true

24. Generating a Range of Numbers

    const range = Array.from({ length: 5 }, (_, i) => i + 1);
    // Output: range = [1, 2, 3, 4, 5]

25. Implementing Promises with Timeout

    const timeout = (promise, ms) => Promise.race([
      promise,
      new Promise((_, reject) => setTimeout(() => reject(new Error("Timeout")), ms))
    ]);
    timeout(fetch('https://api.example.com'), 5000).then(handleResponse).catch(handleError);

26. Extracting File Extension

    const fileName = 'example.png';
    const getFileExtension = str => str.slice(((str.lastIndexOf(".") - 1) >>> 0) + 2);
    // Output: getFileExtension = 'png'

27. Checking if the Current Tab is Focused

    const isTabFocused = () => document.hasFocus();
    // Output: true (if the tab is focused), false otherwise

28. Toggling a Class Name on an Element

    const element = document.querySelector('.my-element');
    const toggleClass = (el, className) => el.classList.toggle(className);
    toggleClass(element, 'active');

These one-liners deliver impactful functionality in a concise manner, perfect for enhancing your JavaScript codebase.

Ref: Mate Marschalko - Medium