What is the first argument passed to node js callback handler?

error
The first argument of the callback handler should be the error and the second argument can be the result of the operation. While calling the callback function if there is an error we can call it like callback(err) otherwise we can call it like callback(null, result).

What is error-first callback in node JS?

Error-First Callback in Node. js is a function which either returns an error object or any successful data returned by the function. The first argument in the function is reserved for the error object. If any error has occurred during the execution of the function, it will be returned by the first argument.

How does callback work in node JS?

js Callback Concept. A callback is a function which is called when a task is completed, thus helps in preventing any kind of blocking and a callback function allows other code to run in the meantime. Callback is called when task get completed and is asynchronous equivalent for a function.

What is callback in node JS Mcq?

What is Callback? Callback is an asynchronous equivalent for a function. Callback is a technique in which a method call back the caller method.

How do you find the argument of a callback function?

4 Answers. To get the list of arguments without breaking functionality, overwrite the callback function in this way: var original = callback; callback = function() { // Do something with arguments: console. log(arguments); return original.

What is arguments in JS?

arguments is an Array -like object accessible inside functions that contains the values of the arguments passed to that function.

What is the first argument at the asynchronous callback?

The first argument of the callback is reserved for an error object. If an error occurred, it will be returned by the first err argument. The second argument of the callback is reserved for any successful response data.

What are the argument passed to the module wrapper function?

This wrapper function has 5 arguments: exports , require , module , __filename , and __dirname . This is what makes them appear to look global when in fact they are specific to each module. All of these arguments get their values when Node executes the wrapper function. exports is defined as a reference to module.

What is the typical first argument to the callback function in node JS What are the argument’s possible values?

Traditionally, the first parameter of the callback is the error value. If the function hits an error, then they typically call the callback with the first parameter being an Error object. If it cleanly exits, then they will call the callback with the first parameter being null and the rest being the return value(s).

What is callback Mcq?

The callback is a technique in which a method calls back the caller method. The callback is an asynchronous equivalent for a function.