Asynchronous Programming and Callbacks

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Questions and Answers

What is the primary issue encountered when attempting to execute the `queryData()` function before the `connectToDatabase()` function?

JavaScript's asynchronous nature doesn't guarantee a specific execution order of functions.
The `queryData()` function might attempt to access the database before a connection is established. (correct)
The `connectToDatabase()` function returns an undefined value, which can cause errors.
The `queryData()` function might be executed multiple times if the `connectToDatabase()` function takes too long.

How is the callback mechanism implemented in the given scenario to ensure correct execution order?

The `queryData()` function is invoked within the `connectToDatabase()` function after the connection is established. (correct)
The `connectToDatabase()` function uses a timeout function to delay the `queryData()` function until the connection is ready.
The `queryData()` function is executed as a separate thread, guaranteeing its execution after the `connectToDatabase()` function.
The `connectToDatabase()` function returns a promise that resolves after the connection is established.

What is the problem encountered when the `queryData()` function is provided as a callback without removing the parentheses after its name?

The callback function is executed synchronously, leading to a blocking operation that delays the `connectToDatabase()` function.
The callback function is not executed at all, resulting in an error when the `connectToDatabase()` function attempts to invoke it.
The callback function is immediately executed, passing its return value (which is `undefined`) to the `connectToDatabase()` function. (correct)
The callback function is executed multiple times, resulting in duplicate queries being sent to the database.

How is the `queryData()` function made more dynamic by adding parameters?

It enables passing different SQL queries to the database through the <code>connectToDatabase()</code> function. (D) Signup and view all the answers

What is the key benefit of passing the query as a parameter to the `connectToDatabase()` function?

It ensures the execution of the <code>queryData()</code> function only after the database connection is established, preventing errors due to premature execution. (A) Signup and view all the answers

What is the main benefit of asynchronous programming in the context of the provided text?

It enables the program to handle long-running tasks without blocking the main execution flow, maintaining responsiveness. (C) Signup and view all the answers

Which of the following best describes a callback function, based on the provided text?

A function that is passed to another function as an argument and is executed within the outer function upon the completion of some asynchronous operation. (A) Signup and view all the answers

In the provided text, what is the purpose of the `setTimeout` function in the example given?

To introduce a delay before a function is executed, demonstrating the asynchronous nature of JavaScript. (C) Signup and view all the answers

The text mentions a function called `connectToDatabase`. What is the purpose of this function in the context of the example provided?

To establish a connection with a database, simulating the asynchronous nature of such an operation. (C) Signup and view all the answers

What is the main reason why the order of console output in the "setTimeout" example is unexpected?

The <code>setTimeout</code> function executes the callback function asynchronously, meaning the program's main execution flow does not wait for the callback function to complete before moving on to the next line of code. (C) Signup and view all the answers

Why is it important to use a callback function when working with asynchronous operations like `connectToDatabase` and `queryData`?

Callback functions allow the program to continue executing other tasks while the asynchronous operation is running, preventing the program from becoming unresponsive. (A) Signup and view all the answers

The text mentions that the `queryData` function takes a random amount of time to complete. Why is this randomness crucial in the context of the example?

The randomness illustrates the real-world scenarios where network latency or database processing times can vary, highlighting the importance of asynchronous programming. (A) Signup and view all the answers

In the example provided, what is the intended order of execution for the `connectToDatabase` and `queryData` functions?

The <code>connectToDatabase</code> function should be executed first, followed by the <code>queryData</code> function, as connecting to the database is a prerequisite for querying data. (C) Signup and view all the answers

Flashcards

Callback Function

A function passed as an argument to another function, to be invoked later.

connectToDatabase()

A function that establishes a connection to a database.