20 Must-Know JavaScript Utility Functions to Boost Productivity

// 1. Generate a random integer between min and max
const randomInt = (min, max) => Math.floor(Math.random() * (max - min + 1)) + min;
scrib.show(randomInt(100,100000))

// 2. Get time ago (e.g., "4 hours ago")
const timeAgo = date => {
  const diff = (new Date() - new Date(date)) / 1000;
  const units = [
    ['year', 31536000], ['month', 2592000],
    ['day', 86400], ['hour', 3600],
    ['minute', 60], ['second', 1]
  ];
  for (let [unit, sec] of units) {
    const val = Math.floor(diff / sec);
    if (val >= 1) return `${val} ${unit}${val > 1 ? 's' : ''} ago`;
  }
  return 'just now';
};
scrib.show(timeAgo("2025/05/12"))

// 3. Format date to YYYY-MM-DD 
const formatDate = date => new Date(date).toISOString().split('T')[0];
scrib.show(formatDate("2025/05/12"))

// 4. Remove duplicates
const unique = arr => [...new Set(arr)];
scrib.show(unique([1,1,2,2,2,3,4,5,5,9]))

// 5. Flatten nested arrays
const flatten = arr => arr.flat(Infinity);
scrib.show(flatten([1,1,[2,2,2],[3,4,[5]],5,9]))

// 6. Shuffle array
const shuffle = arr => arr.sort(() => Math.random() - 0.5);
scrib.show(shuffle([1,1,2,2,2,3,4,5,5,9]))

// 7. Get the intersection of two arrays
const intersect = (a, b) => a.filter(x => b.includes(x));
scrib.show(intersect([1,2,3,4],[1,3,4,5]))

// 8. Capitalize first letter
const capitalize = str => str.charAt(0).toUpperCase() + str.slice(1);
scrib.show(capitalize("mysterio"))

// 9. Slugify a string to create a hyphenated url slug
const slugify = str => str.toLowerCase().trim().replace(/\s+/g, '-').replace(/[^\w\-]+/g, '');
scrib.show(slugify("products and services")) // products-and-services

// 10. Truncate a string
const truncate = (str, len) => str.length > len ? str.slice(0, len) + '...' : str;
scrib.show(truncate("Web development has many frameworks", 25))

// 11. Validating an email
const isEmail = str => /^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(str); // replace regex with your regex
scrib.show(isEmail("mysterio09@gmail.com"))

// 12. Check if an object is empty
const isEmptyObject = obj => Object.keys(obj).length === 0;
scrib.show(isEmptyObject({})) // true
scrib.show(isEmptyObject({ name: "Mysterio" })) // false

// 13. Get query params from URL
const getQueryParams = url => Object.fromEntries(new URL(url).searchParams.entries());
const url = "https://example.com/user?name=mysterio&age=24&country=India";
scrib.show(getQueryParams(url)) // { "name": "mysterio", "age": "24", "country": "India" }

// 14. Serialize object to query string
const toQueryString = obj => new URLSearchParams(obj).toString();
const person = { "name": "mysterio", "age": "24", "country": "India" }
scrib.show(`https://example.com/user?${toQueryString(person)}`)

// 15. Checking for leap year
const isLeapYear = year => new Date(year, 1, 29).getDate() === 29;
scrib.show(isLeapYear("2025-05-15"))

// 16. Remove Falsy Values
const compact = arr => arr.filter(Boolean);
scrib.show(compact([false, undefined, null, 0, 1, 2, 3]))

// 17. Count Occurrences in Array
const countOccurrences = (arr, val) => arr.reduce((a, v) => (v === val ? a + 1 : a), 0);
scrib.show(countOccurrences([1,1,2,2,2,3,4,5,5,9], 2))

// 18. Find Duplicates in Array
const findDuplicates = arr => {
  return [...new Set(arr.filter((item, index) => arr.indexOf(item) !== index))];
};
scrib.show(findDuplicates([1,1,2,2,2,3,4,5,5,9]))

// 19. Check if Value is Numeric
const isNumeric = val => !isNaN(parseFloat(val)) && isFinite(val);
scrib.show(isNumeric(NaN)) // false
scrib.show(isNumeric("24s")) // false
scrib.show(isNumeric("24")) // true
scrib.show(isNumeric(24)) // true
scrib.show(isNumeric(24.45)) // true

// 20. Pick specific keys from an object
const pick = (obj, keys) =>
  keys.reduce((acc, key) => {
    if (key in obj) acc[key] = obj[key];
    return acc;
  }, {});
const person = { "name": "mysterio", "age": "24", "country": "India" }
scrib.show(pick(person, ["name", "age"]))