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JavaScript Questions & Answers – Loops 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) What will be the output of the following JavaScript code? 
function printArray(a)
{
    var len = a.length, i = 0;
     if (len == 0)
        console.log("Empty Array");
     else
     {
         do
         {
             console.log(a[i]);
        } while (++i < len);
     }
}
[A] Prints the numbers in the array in order
[B] Prints the numbers in the array in the reverse order
[C] Prints 0 to the length of the array
[D] Prints “Empty Array”
Answer: Prints the numbers in the array in order
(2) What are the three important manipulations done in a for loop on a loop variable?
[A] Updation, Incrementation, Initialization
[B] Initialization,Testing, Updation
[C] Testing, Updation, Testing
[D] Initialization,Testing, Incrementation
Answer: Initialization,Testing, Updation

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(3) What will the following JavaScript code snippet work? If not, what will be the error? 
function tail(o)
{
    for (; o.next; o = o.next) ;
    return o;
}
[A] No, this will throw an exception as only numerics can be used in a for loop
[B] No, this will not iterate
[C] Yes, this will work
[D] No, this will result in a runtime error with the message “Cannot use Linked List”
Answer: Yes, this will work
(4) What will be the equivalent code of the following JavaScript code? 
for(var p in o)
   	console.log(o[p]);
[A] 
for (var i = 0;i < a.length;i++)
         console.log(a[i]);
[B] 
for (int i = 0;i < a.length;i++)
         console.log(a[i]);
[C] 
for (var i = 0;i <= a.length;i++)
     	console.log(a[i]);
[D] 
for (var i = 1;i < a.length;i++)
     	console.log(a[i]);
Answer: 
for (var i = 0;i < a.length;i++)
    	console.log(a[i]);
(5) One of the special features of an interpreter in reference with the for loop is that ___________
[A] Before each iteration, the interpreter evaluates the variable expression and assigns the name of the property
[B] The iterations can be infinite when an interpreter is used
[C] The body of the loop is executed only once
[D] the iteration is finite when an interpreter is used
Answer: Before each iteration, the interpreter evaluates the variable expression and assigns the name of the property
(6) What will happen if the body of a for/in loop deletes a property that has not yet been enumerated?
[A] The property will be stored in a cache
[B] The loop will not run
[C] That property will not be enumerated
[D] The property will be enumerated
Answer: That property will not be enumerated
(7) What will be the step of the interpreter in a jump statement when an exception is thrown?
[A] The interpreter stops its work
[B] The interpreter throws another exception
[C] The interpreter jumps to the nearest enclosing exception handler
[D] The interpreter throws an error
Answer: The interpreter jumps to the nearest enclosing exception handler
(8) What will be the role of the continue keyword in the following JavaScript code snippet? 
while (a != 0)
{
  if (a == 1)
       continue;
   	else
      	 a++;
}
[A] The continue keyword restarts the loop
[B] The continue keyword skips the next iteration
[C] The continue keyword skips the rest of the statements in that iteration
[D] The continue keyword breaks out of the loop
Answer: The continue keyword skips the rest of the statements in that iteration
(9) What could be the task of the statement debugger in the following JavaScript code? 
function f(o)
{
     if (o === undefined) debugger;
}
[A] It does nothing but a simple breakpoint
[B] It debugs the error in that statement and restarts the statement's execution
[C] It is used as a keyword that debugs the entire program at once
[D] It is used to find error in the statement
Answer: It does nothing but a simple breakpoint
(10) Among the keywords below, which one is not a statement?
[A] debugger
[B] with
[C] if
[D] use strict
Answer: use strict
(11) What will be the output of the following JavaScript code?

function range(int length)

{

int a=5;

for(int i=0;i< length;i++)

{

console.log(a);

}

}

range(3);

[A] 5
[B] 555
[C] 3
[D] error
Answer: 555
(12) What will be the output of the following JavaScript code?

var a = 10;

do {

a += 1;

console.log(a);

} while (a < 5);

[A] 11121314
[B] 1112
[C] 12345
[D] 11
Answer: 11
(13) What will be the output of the following JavaScript code?

var a= 0;

var b = 0;

while (a < 3)

{

a++;

b += a;

console.log(b);

}

[A] 135
[B] 123
[C] 013
[D] 01
Answer: 135
(14) What will be the output of the following JavaScript code?

int size=5;

int a=5;

int size=4;

for(int j=size;j>=0;j--)

{

console.log(a);

a=a-2;

}

[A] 5555
[B] 5321
[C] 531-1
[D] 531
Answer: 531-1
(15) What will be the output of the following JavaScript code?

int a=0;

for(a;a<5;a++);

console.log(a);

[A] 0
[B] error
[C] 4
[D] 5
Answer: 5

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