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1000+ JavaScript Multiple Choice Question Answer [Solved]

Thursday 9th of March 2023

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1. A hexadecimal literal begins with __________
A. 00
B. 0x
C. 0X
D. Both 0x and 0X
Answer : D
2. What will be the output of the following Javascript code?
<script>
var x = 5;
var y = 2;
var z = x % y;
document.getElementById("demo").innerHTML = z;
</script>
A. 0
B. 1
C. 2
D. 5
Answer : B
3. 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
4. The primary purpose of the array map() function is that it __________
A. maps the elements of another array into itself
B. passes each element of the array and returns the necessary mapped elements
C. passes each element of the array on which it is invoked to the function you specify, and returns an array containing the values returned by that function
D. pass the elements of the array into another array
Answer : C
5. Consider the following JavaScript statements.
var text = testing: 1, 2, 3; // Sample text
var pattern = /d+/g // Matches all instances of one or more digits

In order to check if the pattern matches with the string text, the statement is ____________
A. text==pattern
B. text.equals(pattern)
C. text.test(pattern)
D. pattern.test(text)
Answer : D
6. 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
7. 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
8. 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
9. 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
10. What will be the output of the following JavaScript code?
function equalto()
{
int num=10;
if(num===10)
return true;
else
return false;
}
A. true
B. false
C. runtime error
D. compilation error
Answer : A
11. 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 : D
12. 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
13. An expression that can legally appear on the left side of an assignment expression. is a well known explanation for variables, properties of objects, and elements of arrays. They are called ___________
A. Properties
B. Prototypes
C. Lvalue
D. Definition
Answer : C
14. What is the observation made in the following JavaScript code?
var count = [1,,3];
A. The omitted value takes undefined
B. This results in an error
C. This results in an exception
D. The omitted value takes an integer value
Answer : A
15. 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
16. 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
17. The property of a primary expression is ____________
A. stand-alone expressions
B. basic expressions containing all necessary functions
C. contains variable references alone
D. contains only keywords
Answer : A
18. 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
19. 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
20. 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
21. 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
22. 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
23. 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
24. JavaScript Code can be called by using ___________
A. RMI
B. Triggering Event
C. Preprocessor
D. Function/Method
Answer : D
25. 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
26. 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
27. 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
28. 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
29. 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
30. 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
31. 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
32. Which of the operator is used to test if a particular property exists or not?
A. in
B. exist
C. within
D. exists
Answer : A
33. In the following switch syntax, the expression is ompared with the case labels using which of the following operator(s)?
switch(expression)
{
statements
}
A. ==
B. equals
C. equal
D. ===
Answer : D
34. 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
35. What will be the output of the following JavaScript code?
var arr=[1,2,3];
var rev=arr.reverse();
document.writeln(rev);
A. 1, 2, 3
B. 3, 2, 1
C. 3
D. 1
Answer : B
36. 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
37. 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
38. A linkage of series of prototype objects is called as ________
A. prototype stack
B. prototype chain
C. prototype class
D. prototypes
Answer : B
39. 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
40. What will be the output of the following JavaScript code?
const object1 = {
property1: 20
};
console.log(Object.is(object1));
A. 20
B. true
C. false
D. error
Answer : C
41. The script tag must be placed in __________
A. the head tag
B. the head or body
C. the title or head
D. after the body tag
Answer : B
42. 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
43. What will be the output of the following JavaScript code?
var values=[1,2,3,4]
var ans=values.slice(1);
document.writeln(ans);
A. 1, 2, 3, 4
B. 2, 3, 4
C. 1, 3, 4
D. error
Answer : D
44. What will be the output of the following JavaScript code?
var val1=[1,2,3];
var val2=[6,7,8];
var result=val1.concat(val2);
document.writeln(result);
A. 1, 2, 3
B. Error
C. 1, 2, 3, 6, 7, 8
D. 123
Answer : C
45. 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
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. 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
48. 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
49. 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
50. 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
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