Are you trying to debug code and keep running into the aptly-named "TypeError: Callback is Not a Function" error? Fret not! This guide is here to help you understand why this error is appearing and how to fix it.
What is a TypeError?
A TypeError is a type of Error that appears in JavaScript console logs when a variable associated with the function is not of the expected data type. This can mean that you have either declared the variable with an incorrect type or the variable is not interacting correctly with the function.
Why does this error appear?
This particular error occurs because a variable is being passed as an argument to a function that expects a real callback function instead of the variable. When the variable is of a different type than the expected callback, a TypeError is thrown.
How to fix TypeError: Callback is Not a Function?
To resolve this issue, first inspect the code and identify the variable that is being passed to the function. Check the type of the variable and make sure it is a function that is compatible with the function expecting the callback.
If the expected function is expecting an Async task, the callback must return a Promise with the value resolved.
If the variable is not compatible with the expected callback, you should define a new function that meets the compatibility requirements and use it as a callback.
FAQ
Q. What is a TypeError?
A. A TypeError is a type of Error that appears in JavaScript console logs when a variable associated with the function is not of the expected data type. This can mean that you have either declared the variable with an incorrect type or the variable is not interacting correctly with the function.
Q. Why does this error appear?
A. This particular error occurs because a variable is being passed as an argument to a function that expects a real callback function instead of the variable. When the variable is of a different type than the expected callback, a TypeError is thrown.
Q. What type of variable should be passed as a callback?
A. All variables passed as callbacks must be compatible with the expected function. If the expected function is expecting an Async task, the callback must return a Promise with the value resolved.
Q. How to check the type of a variable?
A. JavaScript provides a typeof operator to check the type of a variable. The typeof operator returns the data type of the variable. For example, if the variable is a string, typeof will return “String”.
Q. How to fix TypeError: Callback is Not a Function?
A. To resolve this issue, first inspect the code and identify the variable that is being passed to the function. Check the type of the variable and make sure it is a function that is compatible with the function expecting the callback. If the variable is not compatible with the expected callback, you should define a new function that meets the compatibility requirements and use it as a callback.