Q
What does Object.keys(person) return if var person = {name: 'John', age: 30};?

Answer & Solution

Answer: Option A
Solution:
Object.keys(person) returns an array of the object's own enumerable property names.
Related Questions on Average

How do you create an instance of the Car object using the constructor function?

A). var myCar = new Car('Toyota', 'Corolla');

B). var myCar = Car('Toyota', 'Corolla');

C). var myCar = create Car('Toyota', 'Corolla');

D). var myCar = construct Car('Toyota', 'Corolla');

What will console.log(newCar.make); output if class Car { constructor(make) { this.make = make; }} var newCar = new Car('Honda');?

A). Honda

B). Car

C). Undefined

D). Error

How can you delete the age property from the person object?

A). delete person.age;

B). remove person.age;

C). person.age = null;

D). person.age.delete;

How can you check if the age property exists in the person object?

A). 'age' in person

B). person.has('age')

C). person.contains('age')

D). person.hasOwnProperty('age')

How do you define a method named greet in an object var person = {};?

A). person.greet = function() {};

B). person.greet: function() {};

C). person.greet = () {};

D). person.greet = function {};

How do you define a class in JavaScript ES6?

A). class ClassName { constructor() {} }

B). function ClassName() { constructor() {} }

C). class ClassName() { constructor {} }

D). function class ClassName { constructor() {} }

How do you add a method to an object created with a constructor function?

A). this.methodName = function() {}

B). this.methodName: function() {}

C). this.methodName = () {}

D). this.methodName: () {}

What will console.log(car.make); output if var car = {make: 'Toyota', model: 'Corolla'};?

A). Toyota

B). Corolla

C). Undefined

D). Error

How do you iterate over all properties of an object var person = {name: 'John', age: 30};?

A). for (var key in person)

B). for (var key of person)

C). forEach(key in person)

D). forEach(key of person)

How do you define a method inside a class in JavaScript ES6?

A). methodName() {}

B). this.methodName = function() {}

C). function methodName() {}

D). methodName: function() {}