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JavaScript Questions & Answers – JavaScript Subsets | 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 Crockford’s subset does not include which function in JavaScript?
[A] eval()
[B] coeval()
[C] equal()
[D] equivalent()
Answer: eval()
(2) What does javascript use instead of == and !=?
[A] It uses bitwise checking
[B] It uses === and !== instead
[C] It uses equals() and notequals() instead
[D] It uses equalto()
Answer: It uses === and !== instead

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(3) What is being imposed on each subset to ensure that it conforms to the subset?
[A] A parser to parse the code
[B] A parser that parses and adds to the subset
[C] A static verifier that parses code
[D] A predefined function to parse the code
Answer: A static verifier that parses code
(4) Why was “The Good Parts” designed as a language subset in JavaScript?
[A] To improve programmer flexibility
[B] To balance the workload of the programmer
[C] To create an in-built compiler and interpreter
[D] To improve programmer productivity
Answer: To improve programmer productivity
(5) Which is the subset that is a secure container designed for the purpose of safely running untrusted JavaScript?
[A] Sandbox
[B] The Good Parts
[C] Both Sandbox and Good Parts
[D] Web browser
Answer: Sandbox
(6) Why is this keyword not preferred in JavaScript?
[A] Highly memory consuming
[B] Functions should access the global objects
[C] Functions should not access the global objects
[D] Very inefficient to use
Answer: Functions should not access the global objects
(7) Which are the two functions that are not allowed in any secure subset?
[A] evaluate() and restrict()
[B] eval() and the Function() constructor
[C] debugger() and test()
[D] eval() and debugger()
Answer: debugger() and test()
(8) Which is the object that defines methods that allow complete control over page content?
[A] The client-side document object
[B] The server-side document object
[C] Both client-side and server-side document object
[D] Web document object
Answer: The client-side document object
(9) Which was one of the first security subsets proposed?
[A] FBJS
[B] Caja
[C] dojox.secure
[D] ADSafe
Answer: ADSafe
(10) Which is the subset that transforms web content into secure modules that can be safely hosted on a web page?
[A] Microsoft Web Sandbox
[B] ADsafe
[C] Caja
[D] dojox.secure
Answer: dojox.secure
(11) What will be the output of the following JavaScript code? 
var set = new Set();  
set.add("one");  
set.add("two");    
for (let elements of set) 
{  
    document.writeln(elements+" ");  
}
[A] one
[B] two
[C] one two
[D] undefined
Answer: one two
(12) What will be the output of the following JavaScript code? 
set.add("AngularJS");  
set.add("Bootstrap");    
set.delete("Bootstrap");  
document.writeln(set.size);
[A] 2
[B] 1
[C] 0
[D] Undefined
Answer: 1
(13) What will be the output of the following JavaScript code? 
set.add("one");  
set.add("two");  
set.add("three");    
set.clear();  
document.writeln(set.size);
[A] one
[B] 1
[C] 2
[D] 0
Answer: 0
(14) What will be the output of the following JavaScript code? 
set.add("one");  
set.add("two”);
var itr=set.values();  
document.writeln(itr.next().value);
[A] one
[B] two
[C] error
[D] undefined
Answer: one
(15) What will be the output of the following JavaScript code? 
set.add("1");  
set.add("2");    
document.writeln(set.has("3"));
[A] 3
[B] true
[C] false
[D] 2
Answer: false

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