JS Utility Functions Library | DevToolbox

formatDate(date, fmt)

Date

Formats a date using common display formats with ordinal suffixes.

Try it

16th Mar 26

getDateFromTimestamp(ts)

Date

Converts a Unix timestamp (seconds or ms) to a readable ISO date string.

Try it

2025-03-16 00:00:00

getDaysBetween(d1, d2)new

Date

Returns the number of days between two dates.

Try it

74 day(s) between 2026-01-01 and 2026-03-16

isToday(date)new

Date

Returns true if the given date is today.

Try it

✓ Yes, it's today

startOfDay(date)new

Date

Returns a new Date set to 00:00:00.000 of the given day.

Try it

2026-03-16T00:00:00.000Z

addDays(date, n)new

Date

Adds N days to a date and returns the new Date.

Try it

+7 days → 2026-03-23

timeAgo(date)

Time

Converts a date/timestamp into a relative human-readable string.

Try it

1h ago

formatTime(date, fmt)

Time

Formats time as 12h or 24h with optional seconds.

Try it

1:30 PM

truncate(str, len)

String

Truncates a string to a given length and appends ellipsis.

Try it

The quick brown fox ...

slugify(str)

String

Converts a string to a URL-friendly slug.

Try it

hello-world-this-is-a-test

capitalize(str)

String

Capitalizes the first letter of each word.

Try it

Hello World From Utils

generateId(len)

String

Generates a random alphanumeric ID of the given length.

Try it

zsh6crgqzcfr

formatCurrency(n, currency)

Number

Formats a number as a currency string using Intl.NumberFormat.

Try it

$12,499.50

formatBytes(bytes)

Number

Converts raw bytes to a human-readable size string (KB, MB, GB, TB).

Try it

1.5 MB

clamp(n, min, max)

Number

Clamps a number between min and max inclusive.

Try it

clamp(150, 0, 100) = 100

uniqueBy(arr, key)

Array

Removes duplicate objects from an array by a given key.

Try it

[{"id":1,"n":"A"},{"id":2,"n":"B"}]

groupBy(arr, key)

Array

Groups an array of objects by a given key.

Try it

{"a":[{"type":"a","v":1},{"type":"a","v":3}],"b":[{"type":"b","v":2}]}

chunk(arr, size)new

Array

Splits an array into chunks of the given size.

Try it

[[1,2,3],[4,5,6],[7]]

flatten(arr, depth)new

Array

Flattens a nested array to the specified depth.

Try it

[1,2,3,4,5,6]

sortBy(arr, key, dir)new

Array

Sorts an array of objects by a key, ascending or descending.

Try it

[{"n":"Cal","age":20},{"n":"Bob","age":25},{"n":"Ann","age":30}]

intersection(a, b)new

Array

Returns elements that exist in both arrays.

Try it

[3,4,5] (∩ with [3,4,5,6,7])

deepClone(obj)

Object

Creates a deep clone of an object (no reference sharing).

Try it

{"a":1,"b":{"c":2}}

omit(obj, keys)

Object

Returns a new object with specified keys removed.

Try it

{"id":1,"name":"John"}

debounce(fn, ms)

Object

Delays function execution until after a wait period.

Try it

debounce(fn, 300ms) → fn fires 300ms after last call

pick(obj, keys)new

Object

Returns a new object with only the specified keys.

Try it

{"id":1,"name":"John"}

flattenObject(obj)new

Object

Flattens a deeply nested object to dot-notation keys.

Try it

{"a.b.c":1,"d":2}

mergeDeep(target, source)new

Object

Deep-merges two objects; source values override target.

Try it

mergeDeep(input, {"b":{"y":99,"z":3},"c":4}) → {"a":1,"b":{"x":1,"y":99,"z":3},"c":4}

isEmail(str)

Validation

Validates whether a string is a properly formed email address.

Try it

✓ Valid email

isURL(str)

Validation

Validates whether a string is a valid absolute URL.

Try it

✓ Valid URL

isStrongPassword(str)

Validation

Checks for 8+ chars, uppercase, lowercase, number, and special character.

Try it

✓ Strong password

setStorage(key, value)new

Storage ✦

Saves any value to localStorage as JSON with an optional TTL (time-to-live).

Try it

localStorage unavailable in this context

getStorage(key)new

Storage ✦

Gets a value from localStorage and auto-removes it if expired.

Try it

localStorage unavailable

clearStorage(prefix)new

Storage ✦

Removes all localStorage keys that start with the given prefix.

Try it

localStorage unavailable

getURLParams(url)new

Browser ✦

Parses a URL query string into a plain key-value object.

Try it

{ "page": "2", "sort": "asc", "q": "hello" }

buildURL(base, params)new

Browser ✦

Builds a URL from a base string and a params object.

Try it

https://example.com?page=2&sort=asc&q=hello

setCookie(name, val, days)new

Browser ✦

Sets a browser cookie with an expiry date N days from now.

Try it

document.cookie = "session_id=abc123; expires=Mon, 23 Mar 2026 13:30:47 GMT; path=/"

getCookie(name)new

Browser ✦

Reads a cookie value by name from document.cookie.

Try it

Cookies unavailable

detectDevice()new

Browser ✦

Detects whether the current device is mobile, tablet, or desktop.

Try it

💻 Desktop

copyToClipboard(text)new

Browser ✦

Copies a string to the clipboard using the Clipboard API.

Try it

✓ Copied to clipboard: "Text to copy!"

getScrollPercent()new

Browser ✦

Returns how far the user has scrolled down the page as a 0–100% value.

Try it

—

sleep(ms)

Async ✦

Promise-based delay — use with await in async functions.

Try it

await sleep(1000) → pauses execution for 1000ms

retry(fn, attempts, delay)new

Async ✦

Retries an async function up to N times before throwing the final error.

Try it

retry(fn, 3, 500ms) → tries up to 3× with 500ms gap between each

withTimeout(promise, ms)new

Async ✦

Rejects a promise if it doesn't resolve within the specified ms.

Try it

withTimeout(fetchData(), 5000ms) → rejects if > 5000ms

asyncPool(limit, arr, fn)new

Async ✦

Runs async tasks over an array with a maximum concurrency limit.

Try it

asyncPool(3, items, fn) → max 3 concurrent tasks at a time

randomInt(min, max)new

Random ✦

Returns a random integer between min and max (both inclusive).

Try it

randomInt(1, 100) = 78

randomPick(arr)new

Random ✦

Picks and returns a random element from an array.

Try it

date

shuffle(arr)new

Random ✦

Shuffles an array in-place using the Fisher-Yates algorithm.

Try it

[4,2,5,7,6,3,8,1]

randomColor()new

Random ✦

Generates a random hex color code.

Try it

#0bec48

randomUUID()new

Random ✦

Generates a RFC 4122-compliant UUID v4.

Try it

e7e10321-3955-4d21-86c4-91e20bde6211