Q
What is the result of the expression Object.keys(person).length for the following code snippet?

Answer & Solution

Answer: Option C
Solution:
javascript const person = { name: 'John', age: 30 }; person.address = '123 Main St'; The code adds the address property to the person object, resulting in 3 properties.
Related Questions on Average

How can you change the properties of a constant object in JavaScript?

A). A. Use Object.freeze()

B). B. Use const for each property

C). C. Use the delete keyword to remove properties

D). D. Use dot notation or bracket notation

How can you prevent modifications to the properties of a JavaScript object?

A). A. Use Object.preventExtensions()

B). B. Use const for each property

C). C. Use Object.freeze() to freeze the object

D). D. All of the above

Which statement is true about constant objects in JavaScript?

A). A. The properties of a constant object cannot be changed

B). B. Constant objects are frozen and immutable

C). C. Constant objects cannot have properties added or deleted

D). D. The object reference can be reassigned

What is the output of the following code snippet?

A). A. { x: 10, y: 20 }

B). B. { x: 20, y: 10 }

C). C. { x: 10 }

D). D. Error

What is the correct way to modify a property of a constant object in JavaScript?

A). A. Use the delete keyword

B). B. Use the const keyword for the property

C). C. Use dot notation or bracket notation to access and modify the property

D). D. Use Object.freeze() to freeze the object

Which of the following is a valid way to define a constant object in JavaScript?

A). A. const obj = { a: 1, b: 2 };

B). B. const obj = new Object({ a: 1, b: 2 });

C). C. Both A and B

D). D. None of the above

What happens if you use Object.freeze() on a constant object in JavaScript?

A). A. The object reference becomes mutable

B). B. The properties of the object become immutable

C). C. The object becomes frozen and cannot be modified

D). D. A TypeError is thrown

What is the data type of a constant object in JavaScript?

A). A. Object

B). B. Array

C). C. Function

D). D. String

Which of the following will cause an error when used with a constant object in JavaScript?

A). A. Modifying a property using bracket notation

B). B. Adding a property using dot notation

C). C. Deleting a property

D). D. Reassigning the object reference

Which statement about constant objects in JavaScript is correct?

A). A. Constant objects can have their properties reassigned

B). B. Constant objects cannot have properties added or removed

C). C. Constant objects are only applicable to primitive values

D). D. Constant objects are mutable