Q
What will the following code output? console.log(person['age']); if var person = {name: 'John'};

Answer & Solution

Answer: Option C
Solution:
Accessing a non-existing property of an object returns undefined.
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');

How do you define a constructor function for creating Car objects?

A). function Car(make, model) { this.make = make; this.model = model; }

B). Car(make, model) { this.make = make; this.model = model; }

C). var Car = function(make, model) { this.make = make; this.model = model; };

D). Car = function(make, model) { this.make = make; this.model = model; };

What is the correct way to create an object in JavaScript?

A). var obj = {};

B). var obj = [];

C). var obj = ();

D). var obj = <>;

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')

What is the output of console.log(person.greet()); if var person = {greet: function() {return 'Hello';}};?

A). Hello

B). Undefined

C). Error

D). Hello

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

A). ['name', 'age']

B). ['John', 30]

C). {'name', 'age'}

D). {'John', 30}

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 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 add a new property gender with value male to the person object?

A). person.gender = 'male';

B). person.gender = male;

C). person.gender = ['male'];

D). person[gender] = 'male';