Theo's Typesafe Cult•17mo ago

is this the correct use of usecallback?

  const foo = React.useCallback(() => {
    const clientDate = new Date()
    const utcDate = clientDate.getTime() + clientDate.getTimezoneOffset() * 60000
    const timeOffset = 5.5
    const localDate = new Date(utcDate + 3600000 * timeOffset)
    setDate(localDate)
  }, [])

  React.useEffect(() => {
    foo()
    const timer = setInterval(() => foo(), 1000)
    return () => {
      clearInterval(timer)
    }
  }, [foo])

  const foo = React.useCallback(() => {
    const clientDate = new Date()
    const utcDate = clientDate.getTime() + clientDate.getTimezoneOffset() * 60000
    const timeOffset = 5.5
    const localDate = new Date(utcDate + 3600000 * timeOffset)
    setDate(localDate)
  }, [])

  React.useEffect(() => {
    foo()
    const timer = setInterval(() => foo(), 1000)
    return () => {
      clearInterval(timer)
    }
  }, [foo])

4 Replies

harshcut•17mo ago

also how to check if a function (in this case foo) is recreated or not?

JacobMGEvans•17mo ago

ChatGPT:

Yes, the usage of `useCallback` in your code appears to be correct. `useCallback` is used to memoize a function, so that it is only recreated if any of its dependencies change. In your example, you are providing an empty dependency array `[]` to `useCallback`, indicating that the function `foo` has no dependencies and should remain the same throughout the component's lifecycle.

The `useEffect` hook is then used to trigger the `foo` function initially and set up a timer that calls `foo` every second. By including `foo` in the dependency array of `useEffect`, you ensure that the effect will be re-run whenever `foo` changes.

Overall, your code snippet looks correct and demonstrates the proper usage of `useCallback` and `useEffect`.

Yes, the usage of `useCallback` in your code appears to be correct. `useCallback` is used to memoize a function, so that it is only recreated if any of its dependencies change. In your example, you are providing an empty dependency array `[]` to `useCallback`, indicating that the function `foo` has no dependencies and should remain the same throughout the component's lifecycle.

The `useEffect` hook is then used to trigger the `foo` function initially and set up a timer that calls `foo` every second. By including `foo` in the dependency array of `useEffect`, you ensure that the effect will be re-run whenever `foo` changes.

Overall, your code snippet looks correct and demonstrates the proper usage of `useCallback` and `useEffect`.

More ChatGPT:

To check if a function is being recreated or not, you can add a console.log statement inside the function and observe the logs in the browser's console. Here's an example:

const foo = React.useCallback(() => {
  console.log('foo function called');
  // Rest of your code...
}, []);

React.useEffect(() => {
  foo();
  const timer = setInterval(() => foo(), 1000);
  return () => {
    clearInterval(timer);
  };
}, [foo]);

const foo = React.useCallback(() => {
  console.log('foo function called');
  // Rest of your code...
}, []);

React.useEffect(() => {
  foo();
  const timer = setInterval(() => foo(), 1000);
  return () => {
    clearInterval(timer);
  };
}, [foo]);

When you run your React component with this code, you should see the message 'foo function called' logged in the console every time the foo function is executed. If the function is not recreated, you should see the message only once when the component is initially rendered.

If you see the message logged repeatedly, it means that the foo function is being recreated on every render. However, if you see the message logged only once, it indicates that the function is correctly memoized and not recreated unnecessarily.

JacobMGEvans•17mo ago

You may ask why all the ChatGPT... Simply because of this #2

JacobMGEvans•17mo ago

More indepth is actually the React Docs: https://react.dev/reference/react/useCallback

useCallback – React

The library for web and native user interfaces

Gaming

Programming

is this the correct use of usecallback?