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1000+ JavaScript MCQ for XAT [Solved]

Thursday 9th of March 2023

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1. What will be the output of the following Javascript code?
var txt1 = good;
var txt2 = day;
document.getElementById(demo).innerHTML = txt1 + txt2;

 
A. good day
B. goodday
C. error
D. undefined
Answer : B
2. What will be the output of the following JavaScript code?
var a=5 , b=1
var obj = { a : 10 }
with(obj)
{
alert(b)
}
A. 10
B. Error
C. 1
D. 5
Answer : C
3. What will happen if reverse() and join() methods are used simultaneously?
A. Reverses and stores in the same array
B. Reverses and concatenates the elements of the array
C. Reverses
D. Stores the elements of an array in normal order
Answer : A
4. What happens in the following javaScript code snippet?
var count = 0;
while (count < 10)
{
console.log(count);
count++;
}
A. The values of count are logged or stored in a particular location or storage
B. The value of count from 0 to 9 is displayed in the console
C. An error is displayed
D. An exception is thrown
Answer : B
5. The escape sequence stands for _________
A. Floating numbers
B. Representation of functions that returns a value
C. is not present in JavaScript
D. Form feed
Answer : D
6. Which is a more efficient JavaScript code snippet?
Code 1 :
for(var num=10;num>=1;num--)
{
document.writeln(num);
}

Code 2 :
var num=10;
while(num>=1)
{
document.writeln(num);
num++;
}
A. Code 1
B. Code 2
C. Both Code 1 and Code 2
D. Cannot Compare
Answer : A
7. JavaScript _________ when there is an indefinite or an infinite value during an arithmetic computation.
A. Prints an exception error
B. Prints an overflow error
C. Displays Infinity
D. Prints the value as such
Answer : C
8. Consider the following code snippet.
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);
}
}

What does the above code result?
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 : A
9. What will be the output of the following JavaScript code?
A. 125
B. 25
C. 5
D. Error
Answer : C
10. What will be the output of the following JavaScript code?
function printprops(o)
{
for(var p in o)
console.log(p + : + o[p] +
);
}
A. Prints the contents of each property of o
B. Returns undefined
C. Prints only one property
D. Prints the address of elements
Answer : B
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
D. Error
Answer : B
12. 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 : B
13. A function definition expression can be called as __________
A. Function prototype
B. Function literal
C. Function calling
D. Function declaration
Answer : B
14. What kind of expression is new Point(2,3)?
A. Primary Expression
B. Object Creation Expression
C. Invocation Expression
D. Constructor Calling Expression
Answer : B
15. The statement a===b refers to _________
A. Both a and b are equal in value, type and reference address
B. Both a and b are equal in value
C. Both a and b are equal in value and type
D. There is no such statement
Answer : C
16. What happens in the following javaScript code snippet?
var count = 0;
while (count < 10)
{
console.log(count);
count++;
}
A. The values of count are logged or stored in a particular location or storage
B. The value of count from 0 to 9 is displayed in the console
C. An error is displayed D. An exception is thrown
Answer : B
17. 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 : C
18. What will be the output of the following JavaScript code?
var person =
{
name: Rahul,
getName: function()
{
nreturn this.name;
}
}
var unboundName = person.getName;
var boundName = unboundName.bind(person);
document.writeln(boundName());
A. runtime error;
B. compilation error
C. Rahul
D. undefined
Answer : C
19. 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 : B
20. 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 : A
21. 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 : B
22. Consider the following code snippet.
while (a != 0)
{
if (a == 1)
continue;
else
a++;
}

What will be the role of the continue keyword in the above code snippet?
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 : C
23. When does the function name become optional in JavaScript?
A. When the function is defined as a looping statement
B. When the function is defined as expressions
C. When the function is predefined
D. when the function is called
Answer : B
24. If you have a function f and an object o, you can define a method named m of o with
A. o.m=m.f;
B. o.m=f;
C. o=f.m;
D. o=f;
Answer : B
25. The expression of calling (or executing) a function or method in JavaScript is called ________
A. Primary expression
B. Functional expression
C. Invocation expression
D. Property Access Expression
Answer : C
26. 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 : B
27. Which of the following Attribute is used to include External JS code inside your HTML Document?
A. src
B. ext
C. script
D. link
Answer : A
28. What will the following 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 : C
29. What will be the output of the following JavaScript code?
int a=4;
int b=1;
int c=0;
If(a==b)
document.write(a);
else if(a==c)
document.write(a);
else
document.write(c);
A. 4
B. 1
C. Error
D. 0
Answer : D
30. What will be the shift() output of the following JavaScript code?
var a = [];
a.unshift(1);
a.unshift(22);
a.shift();
a.unshift(3,[4,5]);
a.shift();
a.shift();
a.shift();
A. 1
B. [4,5]
C. [3,4,5]
D. Exception is thrown
Answer : A
31. What will be the output of the following JavaScript code?
function output(option)
{
return (option ? yes : no);
}
bool ans=true;
console.log(output(ans));
A. Yes
B. No
C. Runtime error
D. Compilation error
Answer : A
32. Consider the following code snippet :
function constfuncs()
{
var funcs = [];
for(var i = 0; i < 10; i++)
funcs[i] = function() { return i; };
return funcs;
}
var funcs = constfuncs();
funcs[5]()

What does the last statement return ?
A. 9
B. 0
C. 10
D. None of the mentioned
Answer : C
33. A hexadecimal literal begins with __________
A. 00
B. 0x
C. 0X
D. Both 0x and 0X
Answer : D
34. What is a block statement in JavaScript?
A. conditional block
B. block that contains a single statement
C. both conditional block and a single statement
D. block that combines multiple statements into a single compound statement
Answer : D
35. 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 : A
36. 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 : C
37. What will be the output of the following JavaScript code?
var obj=
{
length:20,
height:35,
}
if (breadth' in obj === false)
{
obj.breadth = 12;
}
console.log(obj.breadth);
A. 20
B. 12
C. undefined
D. error
Answer : B
38. What will be the output of the following JavaScript code?
var grade='B';
var result;
switch(grade)
{
case 'A':
{
result+=10;
break;
}
case 'B':
{
result+= 9;
break;
}
case 'C':
{
result+= 8;
break;
}
default:
result+= 0;
}
document.write(result);
A. 10
B. 9
C. 8
D. 0
Answer : B
39. The reduce and reduceRight methods follow a common operation called __________
A. filter and fold
B. inject and fold
C. finger and fold
D. fold
Answer : B
40. The method or operator used to identify the array is __________
A. isarrayType()
B. ==
C. ===
D. typeof
Answer : D
41. The snippet that has to be used to check if a is not equal to null is _________
A. if(a!=null)
B. if (!a)
C. if(a!null)
D. if(a!==null)
Answer : D
42. What will be the equivalent output of the following JavaScript code snippet?
x = ~-y;
w = x = y = z;
q = a?b:c?d:e?f:g;
A. 
x = ~(-y); w = (x = (y = z));
q = a?b:(c?d:(e?f:g));

B. 
x = a?b:(c?d:(e?f:g));
q = ~(-y); w = (x = (y = z));

C. 
x = (x = (y = z));w = ~(-y);
q = a?b:(c?d:(e?f:g));

D. 
x = ~(-y); w = (x = (y = z));
q = (c?d:(e?f:g));

Answer : A
43. Consider the following code snippet
function f(o)
{
if (o === undefined) debugger;
}

What could be the task of the statement debugger?
A. It does nothing but a simple breakpoint
B. It debugs the error in that statement and restarts the statements 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 : A
44. 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 : C
45. What will happen if a return statement does not have an associated expression?
A. It returns the value 0
B. It will throw an exception
C. It returns the undefined value
D. It will throw an error
Answer : C
46. What will the following 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 : C
47. In the following switch syntax, the expression is compared with the case labels using which of the following operator(s)?
switch(expression)
{
statements
}
A. ==
B. equals
C. equal
D. ===
Answer : D
48. Among the keywords below, which one is not a statement?
A. debugger
B. with
C. if
D. use strict
Answer : D
49. The one-liner code that concatenates all strings passed into a function is
A. 
function concatenate()
{
return String.prototype.concat('', arguments);
}

B. 
function concatenate()
{
return String.prototype.apply('', arguments);
}

C. 
function concatenate()
{
return String.concat.apply('', arguments);
}

D. 
function concatenate()
{
return String.prototype.concat.apply('', arguments);
}

Answer : D
50. JavaScript can be written __________
A. directly into JS file and included into HTML
B. directly on the server page
C. directly into HTML pages
D. directly into the css file
Answer : A
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