The _______ pattern is used to create an instance of an object with some default values.
- Factory
- Prototype
- Singleton
- Observer
The Factory pattern is used to create an instance of an object with some default values. It provides an interface for creating objects in a super factory or a factory method. This pattern is commonly used in JavaScript to create objects.
What is the output of the arithmetic expression 7 / 0 in JavaScript?
- 0
- Infinity
- NaN (Not-a-Number)
- Error
The output of the arithmetic expression 7 / 0 in JavaScript is Infinity. In JavaScript, dividing a number by 0 results in positive or negative infinity depending on the sign of the numerator. Attempting to divide by 0 does not throw an error, but it produces infinity.
Which organization developed JavaScript?
- Microsoft
- Mozilla
- Netscape
- Oracle
JavaScript was developed by Netscape. Brendan Eich created it in 10 days in September 1995. While Netscape is best known for its role in the development of JavaScript, it didn't create other popular languages like Java.
What is a potential downside of using async/await syntax?
- It makes code harder to read and understand.
- It can't be used with Promises.
- It always leads to callback hell.
- It reduces code efficiency.
One potential downside of using async/await is that it can make code harder to read and understand, especially for developers who are not familiar with asynchronous programming. It may lead to nested code blocks, which can be challenging to follow. However, when used correctly, async/await can make asynchronous code more readable.
The _______ method is used to handle errors in Promises.
- .then()
- .catch()
- .resolve()
- .reject()
The correct method to handle errors in Promises is the .catch() method. When a Promise is rejected, the .catch() method is called with the reason for the rejection, allowing you to handle and manage errors in your asynchronous code effectively.
You've encountered a "Callback Hell" in a project you've inherited. What could be a strategic approach to refactor and manage the nested callbacks for better readability and maintainability?
- Refactor using named functions
- Continue using nested callbacks
- Use anonymous arrow functions
- Convert callbacks to Promises
When dealing with "Callback Hell," the strategic approach is to refactor the code using named functions. This technique makes the code more readable and maintainable by breaking down nested callbacks into separate named functions. It enhances code structure and comprehensibility, making it easier to manage complex asynchronous logic.
The mechanism of closing over variables is a core concept in ________ programming in JavaScript.
- Functional
- Object-Oriented
- Asynchronous
- Procedural
The mechanism of closing over variables is a core concept in "Functional" programming in JavaScript. Functional programming promotes the use of pure functions and emphasizes the importance of avoiding mutable state. Closures play a vital role in functional programming by allowing functions to capture and remember the surrounding state.
Arrow functions are not suitable for defining _________ functions.
- async
- generator
- anonymous
- recursive
Arrow functions do not work well for defining generator functions. Generator functions use the function* syntax and rely on the yield keyword, which doesn't behave as expected in arrow functions. Therefore, the correct option is generator.
If a variable is declared inside a block using the let keyword, it is not accessible _________ that block.
- Outside
- After
- Before
- Within
If a variable is declared inside a block using the let keyword, it is not accessible outside that block. This is known as block scope, and it helps prevent unintended variable hoisting and leakage. Variables declared with let are limited to the block in which they are defined.
How can developers handle errors in callbacks to ensure a smooth user experience and debugging?
- Ignore errors to maintain user experience.
- Use global error handlers to catch all errors.
- Log errors and handle them gracefully with try-catch blocks.
- Rely on automatic error handling by JavaScript.
To ensure a smooth user experience and effective debugging, developers should log errors and handle them gracefully using try-catch blocks in the callback functions. Ignoring errors can lead to unexpected issues for users, and relying solely on global error handlers may not provide context-specific error handling. Handling errors within the callback allows developers to respond appropriately to different situations.
Which of the following is NOT a usage of JavaScript?
- Data Analysis
- Fetching & Displaying Data
- Form Validation
- Web Animations
JavaScript is primarily a web-based language used for front-end development to make web pages interactive. Tasks like Web Animations, Form Validation, and Fetching & Displaying Data are core uses. Data Analysis is typically done using languages like Python.
The traditional "for" loop in JavaScript contains ________ main parts separated by semicolons.
- 2
- 3
- 4
- 5
The traditional "for" loop in JavaScript consists of three main parts separated by semicolons. These parts are: initialization (executed once at the beginning), condition (checked before each iteration), and increment (executed after each iteration). The fourth option is incorrect because a "for" loop in JavaScript does not typically have four main parts.