JavaScript (278)

What will be the output of the following code?

var event = {date: "10-03-2020", name: "JavaScript Conference"};
console.log(event.title);

 null

 undefined

 0

 throw an error

JavaScript objects can only have properties. True or false?

var obj = {a: 10};

true

false

What will the following code output to the console?

var person = {name: "John", age: 25};
Object.seal(person);
delete person.age;
console.log(person.age);

 25

 undefined

 null

throw an error

What will the following code output to the console?

var obj = {a: 2, b: 4};
console.log(Object.values(obj));

 [2,4]

 ["a","b"]

 [0,1]

["a", 2, "b", 4]

What will the following code output to the console?

var obj = {x: 3, y: 6};
console.log(Object.keys(obj));

 [3,6]

 ["x","y"]

 [0,1]

throw an error

What will the following code output to the console?

var obj = {a: 1, b: 2};
Object.freeze(obj);
obj.c = 3;
console.log(obj.c);

 3

 undefined

 null

throw an error

What will the following code output to the console?

var x = Object("xyz");
console.log(x.constructor);

 Object

 Function

 String

throw an error

What will the following code output to the console?

var x = new Object(10);
console.log(x.constructor);

 Object

 Number

 Function

throw an error

The prototype inheritance is another name for class-based inheritance. True or false?

 true

 false

What will the following code output to the console?

var Employee = {
  company: "xyz"
}
var emp = Object.create(Employee);
delete Employee.company;
console.log(emp.company);

 undefined

 xyz

 null

 throw an error