useThrottle

Here's an example of a custom hook that uses the useEffect and useRef Hooks to throttle the execution of a function:

import { useState, useEffect, useRef } from 'react'

function useThrottle(fn, delay, dependencies) {
  const [state, setState] = useState(null)
  const timeoutRef = useRef(null)
  const lastExecutedRef = useRef(0)

  const callback = useCallback(
    (...args) => {
      const now = Date.now()
      const timeSinceLastExecution = now - lastExecutedRef.current

      if (!timeoutRef.current && timeSinceLastExecution > delay) {
        setState(fn(...args))
        lastExecutedRef.current = now
      } else if (!timeoutRef.current) {
        timeoutRef.current = setTimeout(() => {
          timeoutRef.current = null
          lastExecutedRef.current = Date.now()
        }, delay - timeSinceLastExecution)
      }
    },
    [fn, delay]
  )

  useEffect(() => {
    callback.dependencies = dependencies
    return () => {
      clearTimeout(timeoutRef.current)
    }
  }, [callback, dependencies])

  return callback
}

This custom hook takes three parameters:

  • fn: The function to be throttled.
  • delay: The delay (in milliseconds) between each invocation of fn.
  • dependencies: The array of dependencies that fn depends on.

The useEffect Hook is used to throttle the function. We use setTimeout to delay the execution of the function, and a useRef Hook to keep track of the timeout ID. We also return a cleanup function to clear the timeout when the component unmounts.

To use this custom hook, you would simply call it in your functional component and pass in the function you want to throttle, the delay between each invocation, and the dependencies that the function depends on:

function MyComponent() {
  const [count, setCount] = useState(0)

  const handleClick = useThrottle(
    () => {
      setCount((prevCount) => prevCount + 1)
    },
    1000,
    [count]
  )

  return (
    <div>
      <button onClick={handleClick}>Click me</button>
      <p>You clicked the button {count} times.</p>
    </div>
  )
}

In this example, we call the useThrottle hook with a function that updates the count state variable when a button is clicked. We pass in a delay of 1000 milliseconds (1 second) between each invocation, and an array with the count state variable as a dependency. This ensures that the function is throttled correctly, even when the state variable changes rapidly.

Codesandbox Example