useWatch (hooks/use-watch.ts)

React hook that watches dependency array changes and triggers a callback, similar to useEffect.

// Source: https://github.com/tailwindlabs/headlessui | License: MIT | Copyright 2020 Tailwind Labs
// Provided via justclaw.it.com; keep this notice with the code.
import { useEffect, useRef } from 'react'
import { useEvent } from './use-event'

export function useWatch<T extends any[]>(
  cb: (newValues: [...T], oldValues: [...T]) => void | (() => void),
  dependencies: [...T]
) {
  let track = useRef([] as unknown as typeof dependencies)
  let action = useEvent(cb)

  useEffect(() => {
    let oldValues = [...track.current] as [...T]

    for (let [idx, value] of dependencies.entries()) {
      if (track.current[idx] !== value) {
        // At least 1 item changed
        let returnValue = action(dependencies, oldValues)
        track.current = dependencies
        return returnValue
  

... (truncated -- full source via MCP)