You are debugging a JavaScript application and notice that the call stack refers to an anonymous function, making it difficult to trace the error. What could you do to make future debugging easier without altering the function's behavior or structure significantly?
- Convert the anonymous function into a named one
- Use a breakpoint in the browser's debugger
- Add more comments to the anonymous function
- Change the code structure to eliminate the function
To make future debugging easier without altering the function's behavior significantly, you can convert the anonymous function into a named one. Giving a function a meaningful name can help you identify it more easily in the call stack and error messages, making debugging less challenging. Renaming the function doesn't alter its behavior or structure but enhances code readability and maintainability.
In what scenario might a do-while loop be preferred over a while loop, considering best practices?
- When you want to ensure the loop body runs at least once, regardless of the condition.
- When you need to perform a specific number of iterations.
- When you want to optimize loop performance for shorter conditions.
- When you want to break out of the loop early based on a condition.
A do-while loop is preferred when you want to ensure that the loop body runs at least once, regardless of the condition. This is useful in scenarios where you need to perform an action before evaluating the loop condition.
In JavaScript, the ________ object represents the eventual
- EventEmitter
- Promise
- Callback
- Observable
In JavaScript, the Promise object represents the eventual completion or failure of an asynchronous operation. Promises are widely used for handling asynchronous tasks, providing a cleaner and more structured way to work with asynchronous code.
Which method is used to select an element by its ID in JavaScript?
- getElementByTag
- getElementById
- getElementByClass
- querySelector
The correct method to select an element by its ID in JavaScript is getElementById. This method retrieves an element by its unique ID attribute. The other options do not select elements by their IDs.
You're attending a tech conference, and a speaker mentions that JavaScript was initially met with skepticism because of its relation to a more established language. Which language are they referring to?
- Java
- C#
- Python
- Ruby
The skepticism surrounding JavaScript's name is due to its early association with Java. JavaScript was initially named "LiveScript" and was renamed to capitalize on Java's popularity. However, the two languages are quite different in terms of their usage and capabilities.
You are debugging a JavaScript application, and you find a variable that seems to be available even after its block has finished executing. What concept of JavaScript allows this to happen?
- Hoisting
- Closure
- Scope
- Shadowing
This behavior is due to the concept of "Closure" in JavaScript. Closures allow functions to maintain access to their lexical scope, even after the outer function has completed execution. This enables the variable to persist and be accessible outside its block.
The _________ method returns all elements in the document with the specified tag name as a NodeList.
- querySelector()
- getElementByTagName()
- getElementsByClassName()
- querySelectorAll()
The getElementByTagName() method returns all elements in the document with the specified tag name as a NodeList. It's important to note that this method is older and less flexible than querySelectorAll(), which can select elements based on more complex criteria.
Which operator is used to get the data type of a variable?
- typeof
- instanceof
- typeofof
- datatype
The typeof operator in JavaScript is used to determine the data type of a variable. For example, you can use it as typeof variableName to obtain a string representing the data type of the variable. It's a helpful tool for debugging and handling different data types dynamically in your code.
How does the "this" keyword behave inside a closure?
- It refers to the global object.
- It captures the value of "this" from the outer scope.
- It is undefined.
- It refers to the function's local scope.
Inside a JavaScript closure, the "this" keyword behaves by capturing the value of "this" from the outer scope where the closure is defined. This behavior is often used to maintain access to the enclosing context's data within the closure, avoiding issues with the global object or undefined values.
When you use the "this" keyword within a method, it refers to _________.
- The method itself
- The global object
- The parent function
- The calling object
When you use the "this" keyword within a method in JavaScript, it refers to the calling object. The calling object is the object on which the method is invoked, and "this" is a reference to that object, allowing you to access its properties and methods.