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JavaScript Skill Exam

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1. Which operator is used for strict equality comparison in JavaScript?

Option: ==

Option: !=

Option: ===

Option: !==

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2. What is the concept of currying in JavaScript and its benefits?

Option: Defining a function that returns a new function with some arguments pre-filled.

Option: A way to optimize function performance.

Option: Related to function hoisting behavior.

Option: Not a valid concept in JavaScript.

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3. How can you achieve immutability in JavaScript objects?

Option: By defining constants using const. (This prevents reassignment of the reference, but nested objects can still be modified)

Option: By using libraries like Immutable.js.

Option: By recursively freezing all nested objects within the main object.

Option: Immutability is not possible in JavaScript.

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4. What is the spread operator (...) used for in JavaScript?

Option: To perform mathematical calculations

Option: To concatenate strings

Option: To spread elements of an iterable into individual arguments or elements within an array or object.

Option: To access DOM elements

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5. Explain the concept of reactive programming in JavaScript and its use cases.

Option: A programming paradigm based on data streams and propagating changes automatically.

Option: Related to asynchronous programming with promises.

Option: A way to manage complex state in applications.

Option: Not a widely used concept in JavaScript. (Requires libraries like RxJS)

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6. What is the syntax for creating a new instance of a class in JavaScript (assuming classes are defined)?

Option: var objectName = new ClassName(parameters);

Option: define objectName = ClassName(parameters);

Option: create objectName = ClassName(parameters);

Option: ClassNam objectName(parameters);

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7. What is the difference between strict mode and non-strict mode in JavaScript?

Option: Strict mode enforces stricter coding practices and catches potential errors.

Option: Strict mode is only used for server-side JavaScript.

Option: Strict mode is slower than non-strict mode.

Option: There is no practical difference.

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8. What are the advantages and disadvantages of using a headless browser like Puppeteer for web scraping or automation tasks?

Option: Advantages: Powerful for complex automation, disadvantages: Requires Node.js setup and can be resource-intensive.

Option: Headless browsers are unreliable for web scraping.

Option: Primarily used for browser testing.

Option: Not recommended for ethical reasons. (Consider website terms of service)

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9. What is the event listener method used to attach an event handler to an element?

Option: onclick

Option: onlisten

Option: attachEvent

Option: bindEvent

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10. What is a closure in JavaScript?

Option: A function that has access to the variable environment of its outer function even after the outer function has returned.

Option: A way to define private variables within a function.

Option: A type of data structure.

Option: A method for handling asynchronous operations.

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11. Explain the concept of code splitting in modern JavaScript frameworks and its advantages.

Option: A technique to load different parts of the application code on demand, reducing initial bundle size and improving perceived performance.

Option: Code splitting increases the complexity of managing application state.

Option: Not recommended for production builds.

Option: Only applicable for server-side rendered applications.

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12. What is the purpose of a web worker in JavaScript?

Option: To run long-running tasks in the background without blocking the main thread.

Option: To improve the visual appearance of a web page.

Option: To handle user input events efficiently.

Option: To share data between different tabs in a browser.

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13. What method is used to sort an array in JavaScript?

Option: sortNumber(array)

Option: sort(array)

Option: arrange(array)

Option: order(array)

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14. How do you write a single-line comment in JavaScript?

Option: // This is a comment

Option: /* This is a comment */

Option: # This is a comment

Option: None of the above

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15. What is the purpose of a Promise object in JavaScript?

Option: To define a function that will be executed later.

Option: To store and manipulate data.

Option: To handle user input validation.

Option: To style HTML elements.

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16. What is the correct way to define a default parameter value in a function?

Option: function name(param = value) { ... }

Option: function name(value = param) { ... }

Option: function name(param := value) { ... }

Option: None of the above

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17. What are the benefits of using TypeScript, a superset of JavaScript, in large-scale projects?

Option: TypeScript adds optional static typing for improved code readability, maintainability, and early error detection.

Option: TypeScript requires a complete rewrite of existing JavaScript code.

Option: Not necessary for projects with good coding practices.

Option: Primarily used for server-side JavaScript with Node.js.

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18. What data type is returned by typeof null in JavaScript?

Option: string

Option: number

Option: object

Option: undefined

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19. What is the purpose of a virtual DOM in libraries like React and how does it improve performance?

Option: A virtual representation of the real DOM that allows for efficient updates by identifying minimal changes before applying them to the real DOM.

Option: The virtual DOM is a separate in-memory database for storing application data.

Option: Not relevant for client-side JavaScript frameworks.

Option: Increases initial page load time.

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20. What are the common methods used to handle errors in asynchronous code with promises?

Option: try...catch block can be used within a promise's then or catch methods.

Option: Error handling is done manually by checking return values.

Option: JavaScript doesn't have built-in error handling for asynchronous code.

Option: All errors are automatically logged to the console.

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FAQ: Free JavaScript Skill Exam Certification

1. What is a JavaScript certification?

A JavaScript certification is a formal acknowledgment of your proficiency in JavaScript, demonstrating that you have the skills and knowledge to develop applications using this programming language.

2. How can I get a JavaScript certification from Microsoft and Google?

3. How do I prepare for a JavaScript certification exam?

To prepare for a JavaScript certification exam, you should: a. Study regularly using online resources and textbooks. b. Practice coding through exercises and real-world projects. c. Participate in coding bootcamps or online courses. d. Engage with study groups or online forums for support and collaboration.

4. What are the benefits of getting a JavaScript certification?

A JavaScript certification can: a. Validate your coding skills and knowledge. b. Enhance your resume and increase job opportunities. c. Potentially lead to higher salaries and career advancement. d. Provide a structured learning path and ensure you meet industry standards.

5. Can I take the JavaScript certification exam online?

Yes, most JavaScript certification exams can be taken online. Platforms like freeCodeCamp, Coursera, and Udemy offer online exams that you can complete from the comfort of your home.

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JavaScript certification exam

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JavaScript certification course

FAQ: Free JavaScript Skill Exam Certification

1. What is a JavaScript certification?

2. How can I get a JavaScript certification from Microsoft and Google?

3. How do I prepare for a JavaScript certification exam?

4. What are the benefits of getting a JavaScript certification?

5. Can I take the JavaScript certification exam online?

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