Callback is not a function ошибка

The “typeerror: callback is not a function” is an error message that occurs in JavaScript.

This article will help you learn, understand, and fix this error.

Remember that it is crucial to understand the error first before proceeding to the steps to fix it.

So, without further ado, let us start with understanding this error.

As mentioned in our first sentence, typeerror: callback is not a function is an error message that occurs in JavaScript.

This error occurs when a function’s callback argument is given, but the function is called without passing the callback as a parameter.

Here is a sample code that causes this error:

function sample(callback) {
  return callback();
}
sample();

Error:

index.js:2
  return callback();
         ^

TypeError: callback is not a function

To fix this error, follow the guide below.

Typeerror: callback is not a function – SOLUTION

Fixing the typeerror: callback is not a function may sound frustrating, but it is easy and quick.

See the sample code below to help you fix the error you are facing.

Sample code:

function sample(callback = () => {}){
 return callback();
}
sample();

Aside from the sample code above, you can also fix it using this code:

function sample(callback) {
 return callback();
}
sample(() => {
  console.log('This is a success!');
});

Output:

This is a success!

If you only want to test a code, use our online JavaScript compiler. In there, you can run JS code online for free.

FAQs

Conclusion

In conclusion, the typeerror: callback is not a function occurs in JavaScript as an error message.

You can solve this error by using the arrow function to define the callback() function, then returning it to the callback() function.

By following the guide above, you will surely solve this error quickly.

That is all for this tutorial, IT source coders!

We hope you have learned a lot from this. Have fun coding!

Thank you for reading! 😊

Comments

It seems that we have a dep to an old version of
scheduler that doesn't work very well with React Hook

see this issue: facebook/react#15647

It seems that we have a dep to an old version of
scheduler that doesn't work very well with React Hook

see this issue: facebook/react#15647

Answer by Hadleigh Parker

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i.e. Instead of…

const [result] = await mySoapClient.Perform_Operation({ ... })

I needed to append the word Async to the method. e.g.

const [result] = await mySoapClient.Perform_OperationAsync({ ... })

Answer by Heath Xiong

I’ll get around to trying method calls and seeing if that works some other time. Bit tired with this issue.,This error can be reproduced (I think) if the server is closed and then opened again quickly. Which makes me think it has something to do with the twitter server. Also sometimes this error is being returned kind of randomly. Maybe it has to do with the timeout function / reconnect logic?:,Not entirely sure how to get around this, might have to do something with uncaughtException.

/var/www/html/01014.org/public_html/srv/node_modules/needle/lib/needle.js:468
      return callback(err, resp, resp ? resp.body : undefined);
             ^

TypeError: callback is not a function
    at done (/var/www/html/01014.org/public_html/srv/node_modules/needle/lib/needle.js:468:14)
    at PassThrough.<anonymous> (/var/www/html/01014.org/public_html/srv/node_modules/needle/lib/needle.js:719:9)
    at PassThrough.emit (events.js:315:20)
    at endReadableNT (_stream_readable.js:1220:12)
    at processTicksAndRejections (internal/process/task_queues.js:84:21)

Answer by Ronan Benitez

I have plenty more content planned for the future, so if you found this helpful and want to receive it directly to your inbox without having to remember to check back here, sign up below:,But what if we wanted to convert a callback function directly to an async/await version of that function? Without using Promises directly?,If we don’t pass in a callback, we get a TypeError: callback is not a function error.

const callbackFn = (firstName, callback) => {
  setTimeout(() => {
    if (!firstName) return callback(new Error('no first name passed in!'))

    const fullName = `${firstName} Doe`

    return callback(fullName)
  }, 2000)
}

callbackFn('John', console.log)
callbackFn(null, console.log)

And here’s the Promise-based version of that function:

const promiseFn = firstName => {
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      if (!firstName) reject(new Error('no first name passed in!'))

      const fullName = `${firstName} Doe`  

      resolve(fullName)
    }, 2000)
  })
}

promiseFn('Jane').then(console.log)
promiseFn().catch(console.log)

The great thing about having our function in Promise form is that we don’t actually need to «make it an async/await version» if we don’t want to. When we call/execute the function, we can simply use the async/await keyword, like so:

const result = (async () => {
  try {
    console.log(await promiseFn('Jim')) 
  } catch (e) {
    console.log(e)
  }

  try {
    console.log(await promiseFn()) 
  } catch (e) {
    console.log(e)
  }
})()

async/await is syntactic sugar around Promises, so it uses them under the hood. Here’s how you can convert it:

const timeout = ms => {
  return new Promise(resolve => setTimeout(resolve, ms))
}

const asyncAwaitFn = async firstName => {
  await timeout(2000) // using timeout like this makes it easier to demonstrate callback -> async/await conversion

  if (!firstName) throw new Error('no first name passed in!')

  const fullName = `${firstName} Doe`

  return fullName
}

const res = (async () => {
  try {
    console.log(await asyncAwaitFn('Jack')) 
  } catch (e) {
    console.log(e)
  }

  try {
    console.log(await asyncAwaitFn()) 
  } catch (e) {
    console.log(e)
  }
})()

Answer by Charlotte Allison

Answer by Rex Parra

Answer by Norah Palacios