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JavaScript Questions & Answers – Classes in JavaScript | JavaScript MCQs

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Free download in PDF JavaScript Multiple Choice Questions and Answers for competitive exams. These short objective type questions with answers are very important for Board exams as well as competitive exams like UPSC, NDA, SSC etc. These short solved questions or quizzes are provided by Gkseries./p>

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(1) The behaviour of the instances present of a class inside a method is defined by __________
[A] Method
[B] Classes
[C] Interfaces
[D] Classes and Interfaces
Answer: Classes
(2) The keyword or the property that you use to refer to an object through which they were invoked is _________
[A] from
[B] to
[C] this
[D] object
Answer: this

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(3) What will be the output of the following JavaScript code? 
var o = new F();
o.constructor === F
[A] false
[B] true
[C] 0
[D] 1
Answer: true
(4) The basic difference between JavaScript and Java is _________
[A] There is no difference
[B] Functions are considered as fields
[C] Variables are specific
[D] Functions are values, and there is no hard distinction between methods and fields
Answer: Functions are values, and there is no hard distinction between methods and fields
(5) The meaning for Augmenting classes is that ___________
[A] objects inherit prototype properties even in a dynamic state
[B] objects inherit prototype properties only in a dynamic state
[C] objects inherit prototype properties in the static state
[D] object doesn’t inherit prototype properties in the static state
Answer: objects inherit prototype properties even in a dynamic state
(6) The property of JSON() method is __________
[A] it can be invoked manually as object.JSON()
[B] it will be automatically invoked by the compiler
[C] it is invoked automatically by the JSON.stringify() method
[D] it cannot be invoked in any form
Answer: it is invoked automatically by the JSON.stringify() method
(7) When a class B can extend another class A, we say that?
[A] A is the superclass and B is the subclass
[B] B is the superclass and A is the subclass
[C] Both A and B are the superclass
[D] Both A and B are the subclass
Answer: A is the superclass and B is the subclass
(8) If A is the superclass and B is the subclass, then subclass inheriting the superclass can be represented as _________
[A] B=inherit(A);
[B] B=A.inherit();
[C] B.prototype=inherit(A);
[D] B.prototype=inherit(A.prototype);
Answer: B.prototype=inherit(A);
(9) The snippet that filters the filtered set is __________
[A] var t=new FilteredSet(s, {function(s) {return !(x instanceof Set);});
[B] var t=new FilteredSet{function(s) {return !(x instanceof Set);});
[C] var t=new FilteredSet(s, {function(s) {return (x instanceof Set);});
[D] var t=new FilteredSet(s, {function(s) {return x;});
Answer: var t=new FilteredSet(s, {function(s) {return !(x instanceof Set);});
(10) The method that can be used to create new properties and also to modify the attributes of existing properties is _________
[A] Object.defineProperty()
[B] Object.defineProperties()
[C] Both Object.defineProperty() and Object.defineProperties()
[D] Object.inherit()
Answer: Both Object.defineProperty() and Object.defineProperties()
(11) What will be the output of the following JavaScript code? 
const obj1 = 
{  
  	a: 10,  
  	b: 15,  
  	c: 18  
};  
const obj2 = Object.assign({c: 7, d: 1}, obj1);  
console.log(obj2.c, obj2.d);
[A] 7,1
[B] 18,1
[C] Undefined
[D] Error
Answer: 7,1
(12) What will be the output of the following JavaScript code? 
function person()
{  
        this.name = 'rahul';  
}  
function obj() 
{  
       obj.call(this)  
}  
obj.prototype = Object.create(person.prototype);  
const app = new obj();  
console.log(app.name);
[A] undefined
[B] runtime error
[C] compilation error
[D] rahul
Answer: rahul
(13) What will be the output of the following JavaScript code? 
const object1 = {};  
Object.defineProperties(object1,
{  
  	property1: 
        {  
             value: 10 
        }  
 });  
console.log(object1.property1);
[A] 0
[B] 10
[C] undefined
[D] error
Answer: 10
(14) What will be the output of the following JavaScript code? 
const prototype1 = {};  
const object1 = Object.create(prototype1);  
console.log(Object.getPrototypeOf(object1) === prototype1);
[A] true
[B] false
[C] error
[D] 0
Answer: true
(15) What will be the output of the following JavaScript code? 
const obj1 = {  
  property1: 2  
};  
Object.seal(object1);    
obj1.property1 =4;  
console.log(obj1.property1);  
delete obj1.property1;
[A] 2
[B] 4
[C] Error
[D] Undefined
Answer: Error

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