Home

JavaScript 1000+ MCQ with answer for CAT

Thursday 9th of March 2023

Sharing is caring

Downlaod JavaScript MCQ PDF
1. 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
2. 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
3. JavaScript Code can be called by using ____________
A. RMI
B. Triggering Event
C. Preprocessor
D. Function/Method
Answer : D
4. 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
5. What will be the output of the following JavaScript code?
int a==2;
int b=4;
int ans=a+b;
print(ans);
A. 2
B. 6
C. 0
D. error
Answer : D
6. 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
D. Floating point
Answer : B
7. 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
8. What will be the output of the following JavaScript code?
function height()
{
var height = 123.56;
var type = (height>=190) ? tall : short;
return type;
}
A. 123.56
B. 190
C. tall
D. short
Answer : D
9. What is the difference between the two lines given below ?
!!(obj1 && obj2);
(obj1 && obj2);
A. Both the lines result in a boolean value True
B. Both the lines result in a boolean value False
C. Both the lines checks just for the existence of the object alone
D. The first line results in a real boolean value whereas the second line merely checks for the existence of the objects
Answer : D
10. What will be the output of the following Javascript code?
var add=new Function(num1,num2,return num1+num2);
document.writeln(add(2,5));
A. 2
B. 5
C. Error
D. 7
Answer : D
11. 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
12. 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
13. Consider the following code snippet.
for(var p in o)
console.log(o[p]);

The above code is equivalent to which code?
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 : A
14. The enumeration order becomes implementation dependent and non-interoperable if ___________
A. If the object inherits enumerable properties
B. The object does not have the properties present in the integer array indices
C. The delete keyword is never used
D. Object.defineProperty() is not used
Answer : A
15. 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
16. 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
17. JavaScript is ideal to ________
A. make computations in HTML simpler
B. minimize storage requirements on the web server
C. increase the download time for the client
D. increase the loading time of the website
Answer : B
18. A conditional expression is also called a _______________
A. Alternative to if-else
B. Immediate if
C. If-then-else statement
D. Switch statement
Answer : B
19. The enumeration order becomes implementation dependent and non-interoperable if ___________
A. If the object inherits enumerable properties
B. The object does not have the properties present in the integer array indices
C. The delete keyword is never used
D. Object.defineProperty() is not used
Answer : A
20. 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
21. 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
22. 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
23. The object has three object attributes namely ________
A. Class, parameters, objects extensible flag
B. Prototype, class, objects parameters
C. Prototype, class, objects extensible flag
D. Native object, Classes and Interfaces and Objects extensible flag
Answer : C
24. 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
25. 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
26. 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 : A
27. What will be the output of the following JavaScript code?
Int a=1;
if(a>10)
{
document.write(10);
}
else
{
document.write(a);
}
A. 10
B. 0
C. 1
D. Undefined
Answer : C
28. When an empty statement is encountered, a JavaScript interpreter __________
A. Ignores the statement
B. Prompts to complete the statement
C. Throws an error
D. Shows a warning
Answer : A
29. What will be the output of the following JavaScript code?
function compare()
{
int num=2;
char b=2;
if(a==b)
return true;
else
return false;
}
A. true
B. false
C. runtime error
D. compilation error
Answer : A
30. What will be the output of the following JavaScript code?
function code(id,name)
{
this.id = id;
this.name = name;
}
function pcode(id,name)
{
code.call(this,id,name);
}
document.writeln(new pcode(101,vivek).id);
A. vivek
B. 101
C. Runtime error
D. Compilation error
Answer : B
31. What will be the output of the following JavaScript code?
var pow=new Function(num1,num2,return Math.pow(num1,num2));
document.writeln(pow(2,3));
A. 2
B. 3
C. 8
D. error
Answer : C
32. Which keyword is used to define the function in javascript?
A. void
B. int
C. function
D. main
Answer : C
33. 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
34. What will be the output of the following JavaScript code?
function output(object)
{
var place=object ? object.place : Italy;
return clean:+ place;
}
console.log(output({place:India}));
A. clean:India
B. clean:Italy
C. error
D. undefined
Answer : A
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. What will be the output of the following JavaScript code?
int a=1;
if(a!=null)
return 1;
else
return 0;
A. 1
B. 0
C. runtime error
D. compiler error
Answer : A
37. 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
38. 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
39. The method or operator used to identify the array is __________
A. isarrayType()
B. ==
C. ===
D. typeof
Answer : D
40. What will be the output of the following JavaScript code?
var string1 = 123;
var intvalue = 123;
alert( string1 + intvalue );
A. 123246
B. 246
C. 123123
D. Exception
Answer : C
41. The web development environment (JavaScript) offers which standard construct for data validation of the input entered by the user.
A. Controlled loop constructs
B. Case checking constructs
C. Validation constructs
D. All of the mentioned
Answer : D
42. 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
43. 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
44. 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 : C
45. 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
46. What will be the output of the following JavaScript code?
var grade='E';
var result;
switch(grade)
{
case 'A':
result+=10;
case 'B':
result+= 9;
case 'C':
result+= 8;
default:
result+= 0;
}
document.write(result);
A. 10
B. 0
C. 18
D. 17
Answer : B
47. What will be the output of the following JavaScript code?
int sum=0;
var arr = [10,15,20,30];
arr.forEach(function myFunction(element)
{
sum= sum+element;
});
document.writeln(sum);
A. 70
B. 75
C. 10
D. error
Answer : B
48. What will be the output of the following Javascript code?
<script>br>txt1 = “ one”;
txt1 += “two”;
document.getElementById("demo").innerHTML = txt1;
</script>
A. onetwo
B. one two
C. error
D. undefined
Answer : A
49. Which is an equivalent code to invoke a function m of class o that expects two arguments x and y?
A. o(x,y);
B. o.m(x) && o.m(y);
C. m(x,y);
D. o.m(x,y);
Answer : D
50. 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
Downlaod JavaScript MCQ PDF

Sharing is caring

Related Post