How does the pop() method behave when applied on an empty array?
- It returns undefined and does nothing
- It throws an error
- It removes the last undefined element and returns it
- It returns null
When the pop() method is applied to an empty array in JavaScript, it returns undefined and does nothing to the array. There are no elements to remove, so it simply returns undefined without causing any errors.
Which method is used to convert a JSON response to a JavaScript object?
- parseJSON()
- toJSON()
- JSON.parse()
- stringifyJSON()
The correct method to convert a JSON response to a JavaScript object is JSON.parse(). JSON.parse() parses a JSON-formatted string and turns it into a JavaScript object. It's commonly used when dealing with data received from APIs or when working with JSON data in JavaScript applications.
Which object is heavily used in AJAX to interact with server-side data?
- XMLHttpRequest
- JSON
- DOM
- Console
XMLHttpRequest is a crucial object used in AJAX (Asynchronous JavaScript and XML) to make HTTP requests to the server and interact with server-side data without requiring a page reload. It allows for asynchronous communication with the server, making web applications more dynamic and responsive.
What is the impact on performance when using a while loop with a condition that evaluates an expression involving function calls?
- High performance impact
- Moderate performance impact
- Low performance impact
- No performance impact
Using a while loop with a condition that involves function calls can have a moderate performance impact. This is because the function calls are evaluated in each iteration, potentially incurring additional processing overhead. It's important to optimize such code to minimize performance issues.
Considering JavaScript's type coercion, what will be the result of [] == ![]?
- TRUE
- FALSE
- undefined
- Throws an error
JavaScript performs type coercion when comparing values. In this case, the empty array [] is truthy, and ![] evaluates to false. When comparing, the empty array is coerced to false, resulting in true. This behavior can be surprising and is a common gotcha in JavaScript.
In what year was JavaScript introduced to the world?
- 1990
- 1995
- 2000
- 2005
JavaScript was introduced to the world in 1995. It was first released as part of Netscape Navigator 2.0. This event marked the beginning of JavaScript's journey as a popular and widely used scripting language for web development.
Which comparison operator performs type coercion if the operands are of different types?
- == (Equality)
- === (Strict Equality)
- != (Inequality)
- !== (Strict Inequality)
The comparison operator == (Equality) performs type coercion if the operands are of different types. This means JavaScript will attempt to convert the operands to the same type before making the comparison. In contrast, === (Strict Equality) checks both value and type without coercion.
Which of the following best describes a JavaScript callback function?
- A function passed as an argument to another function and executed later
- A function used to display pop-up messages
- A function that runs immediately after it's defined
- A function that loops through an array
A JavaScript callback function is a function that is passed as an argument to another function and is executed later, often after the completion of an asynchronous operation. It's a fundamental concept for handling asynchronous tasks and allows for flexible and event-driven programming.
Question 1: You are developing a web application and notice that when user-generated content is displayed on the page, it interprets HTML and JavaScript code. How can you prevent this behavior and enhance security?
- Use the innerText property for rendering
- Implement input validation and sanitization
- Disable JavaScript in the browser
- Use a stronger password policy
The most effective way to prevent user-generated content from executing JavaScript and potentially harmful code is to implement input validation and sanitization. By validating and sanitizing user inputs, you can strip or escape any potentially malicious code, making the content safe for display. Disabling JavaScript altogether may impact the functionality of your web application.
How does the prototype property behave in arrow functions?
- Arrow functions have a prototype property.
- Arrow functions do not have a prototype.
- Arrow functions inherit their prototype.
- Arrow functions override their prototype.
Arrow functions do not have their own this context and do not have a prototype property. Unlike regular functions, arrow functions do not bind their own this value or have a prototype property. This is a key difference to keep in mind when choosing between regular functions and arrow functions in JavaScript.