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1000+ JavaScript Multiple Choice Question Answer [Solved]

Thursday 9th of March 2023

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1. What is the observation made in the following JavaScript code?
if (!a[i]) continue;
A. Skips the defined elements
B. Skips the existent elements
C. Skips the null elements
D. Skips the defined & existent elements
Answer : C
2. 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
3. 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
4. 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
5. 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
6. 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
7. The var and function are __________
A. Keywords
B. Declaration statements
C. Data types
D. Prototypes
Answer : B
8. What will be the output of the following JavaScript code?
var grade='A';
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. 27
C. 8
D. 0
Answer : B
9. Do functions in JavaScript necessarily return a value?
A. It is mandatory
B. Not necessary
C. Few functions return values by default
D. some functions do not return any value
Answer : C
10. Consider the following code snippet :
var tensquared = (function(x) {return x*x;}(10));

Will the above code work ?
A. Yes, perfectly
B. Error
C. Exception will be thrown
D. Memory leak
Answer : A
11. The main purpose of a Live Wire in NetScape is to ________
A. Create linkage between client side and server side
B. Permit server side, JavaScript code, to connect to RDBMS
C. Support only non relational database
D. To interpret JavaScript code
Answer : B
12. Assume that we have to convert false that is a non-string to string. The command that we use is (without invoking the new operator).
A. false.toString()
B. String(false)
C. String newvariable=false
D. Both false.toString() and String(false)
Answer : D
13. 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
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 : C
15. 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
16. JavaScript is a _______________ language.
A. Object-Oriented
B. High-level
C. Assembly-language
D. Object-Based
Answer : D
17. 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 : /strong> C
18. A JavaScript program developed on a Unix Machine ________
A. will throw errors and exceptions
B. must be restricted to a Unix Machine only
C. will work perfectly well on a Windows Machine
D. will be displayed as a JavaScript text on the browser
Answer : C
19. Which attribute is used to specify that the script is executed when the page has finished parsing? (only for external scripts)
A. parse
B. a sync
C. defer
D. type
Answer : C
20. What will be the possible output of the following JavaScript code?
var a = [1,2,3,4,5];
a.slice(0,3);
A. Returns [1,2,3]
B. Returns [4,5]
C. Returns [1,2,3,4]
D. Returns [1,2,3,4,5]
Answer : C
21. 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
22. 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
23. 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
24. One of the special feature 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 : A
25. What will be the output of the following JavaScript code?
string a = hi;
string b =there;
alert(a+b);
A. hi
B. there
C. hithere
D. undefined
Answer : C
26. Consider the following code snippet :
var string2Num=parseInt(123xyz);

The result for the above code snippet would be :
A. 123
B. 123xyz
C. Exception
D. NaN
Answer : A
27. 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
28. 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
29. 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
30. 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
31. 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 : C
32. Which of the following is not considered as an error in JavaScript?
A. Syntax error
B. Missing of semicolons
C. Division by zero
D. Missing of Bracket
Answer : C
33. 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
34. 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
35. What will be the output of the following JavaScript code?
A. 1.01
B. 1.047
C. 1.00
D. 1.4
Answer : B
38. What will be the output of the following Javascript code?
<script>
var x = 10;
x *= 5;
document.getElementById("demo").innerHTML = x;
</script>
A. 5
B. 10
C. 50
D. Error
Answer : C
39. 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
40. The pop() method of the array does which of the following task?
A. decrements the total length by 1
B. increments the total length by 1
C. prints the first element but no effect on the length
D. updates the element
Answer : A
41. 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
42. The type of a variable that is volatile is _______________
A. Volatile variable
B. Mutable variable
C. Immutable variable
D. Dynamic variable
Answer : B
43. 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 : D
44. 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
45. 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
46. The function definitions in JavaScript begins with _____________
A. Identifier and Parentheses
B. Return type and Identifier
C. Return type, Function keyword, Identifier and Parentheses
D. Identifier and Return type
Answer : C
47. 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
48. 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
49. What will be the equivalent code of the following JavaScript code?
o.m(x,y);
A. o.m(x) && o.m(y);
B. o[m](x,y);
C. o(m)[x,y];
D. o.m(x && y);
Answer : B
50. Among the keywords below, which one is not a statement?
A. debugger
B. with
C. if
D. use strict
Answer : D
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