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JavaScript Questions & Answers – Object Attributes and Serialization | 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 unordered collection of properties, each of which has a name and a value is called _________
[A] String
[B] Object
[C] Serialized Object
[D] Array
Answer: Object
(2) The object has three object attributes namely ________
[A] Class, parameters, object’s extensible flag
[B] Prototype, class, objects’ parameters
[C] Prototype, class, object’s extensible flag
[D] Native object, Classes and Interfaces and Object’s extensible flag
Answer: Prototype, class, object’s extensible flag

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(3) What will be the firstname and surname of the following JavaScript code? 
var book = {
             	"main title": "JavaScript", 
              	'sub-title': "The Definitive Guide",
              	"for": "all audiences", 
             	author: { 
                        	firstname: "David",
                        	surname: "Flanagan"
                      }
       			};
[A] properties
[B] property values
[C] property names
[B] objects
Answer: property names
(4) A linkage of series of prototype objects is called as ________
[A] prototype stack
[B] prototype chain
[C] prototype class
[D] prototypes
Answer: prototype chain
(5) In the following syntax, the data type within the square brackets must be ___________

book[datatype]=assignment_value;

[A] An integer
[B] A String
[C] An object
[B] Floating point
Answer: A String
(6) To determine whether one object is the prototype of (or is part of the prototype chain of) another object, one should use the ____________
[A] isPrototypeOf() method
[B] equals() method
[C] === operator
[D] ==opertor
Answer: isPrototypeOf() method
(7) What is the prototype represents in the following JavaScript code snippet?

function f() {};

[A] Function f
[B] A custom constructor
[C] Prototype of a function
[D] Not valid
Answer: A custom constructor
(8) The purpose of extensible attribute is to __________
[A] make all of the own properties of that object non configurable
[B] to configure and bring a writable property
[C] “lock down” objects into a known state and prevent outside tampering
[D] to include new properties into the object
Answer: “lock down” objects into a known state and prevent outside tampering
(9) Identify the process done in the following JavaScript code snippet?

o = {x:1, y:{z:[false,null,""]}};

s = JSON.stringify(o);

p = JSON.parse(s);

[A] Object Encapsulation
[B] Object Serialization
[C] Object Abstraction
[D] Object Encoding
Answer: Object Serialization
(10) The basic purpose of the toLocaleString() is to _________
[A] return a localised object representation
[B] return a parsed string
[C] return a local time in the string format
[D] return a localized string representation of the object
Answer: return a localized string representation of the object
(11) What will be the output of the following JavaScript code? 
const object1 = {};
a = Symbol('a');  
b = Symbol.for('b');
object1[a] = 'harry'; 
object1[b] = 'derry';>
const objectSymbols = Object.getOwnPropertySymbols(object1);
console.log(objectSymbols.length);
[A] 0
[B] 2
[C] 1
[B] error
Answer: 2
(12) What will be the output of the following JavaScript code? 
const obj1 =
{ 
    property1: 21
	} 
const descriptor1 = Object.getOwnPropertyDescriptor(obj1, 'property1');  
console.log(descriptor1.configurable);
console.log(descriptor1.enumerable);
[A] true 21
[B] true false
[C] true true
[D] false false
Answer: true true
(13) What will be the output of the following JavaScript code?

const obj1 = { property1: '10'};

const obj2 = Object.freeze(obj1);

obj2.property1 = '20';

console.log(obj2.property1);

[A] 10
[B] 20
[C] Runtime error
[D] Compilation error
Answer: 10
(14) What will be the output of the following JavaScript code? 
const object1 = {
 	 property1: 20
	}; 
	console.log(Object.is(object1));
[A] 20
[B] true
[C] false
[D] error
Answer: false
(15) What will be the output of the following JavaScript code? 
const obj = {prop: 12};
Object.preventExtensions(obj);
console.log( Object.isExtensible(obj));
[A] 12
[B] false
[C] true
[D] error
Answer: false

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