What will be the output of the following JavaScript code?
var a1 = [,,,];
var a2 = new Array(3);
0 in a1
0 in a2
var a2 = new Array(3);
0 in a1
0 in a2
true false
false true
true true
false true
Correct Answer :
A. true false
Explanation: Array a1 is defined with null values. Therefore we can access the indexes 0, 1 and 2. But array a2 is only defined not declared. Therefore we cannot access index 0.
Related Questions
The script tag must be placed in __________
the head tag
the head or body
the title or head
after the body tag
What will be the output of the following JavaScript code?
function info()
{
int a=1;
int b=2;
return a*b;
}
document.write(info());
{
int a=1;
int b=2;
return a*b;
}
document.write(info());
1
2
3
error
Consider the following code snippet :
var grand_Total=eval(10*10+5);
The output for the above statement would be :
10*10+5
105 as a string
105 as an integer value
Exception is thrown
What will be the output of the following JavaScript code?
function equalto()
{
int num=10;
if(num===10)
return true;
else
return false;
}
{
int num=10;
if(num===10)
return true;
else
return false;
}
true
false
runtime error
compilation error
The main purpose of a Live Wire in NetScape is to ________
Create linkage between client side and server side
Permit server side, JavaScript code, to connect to RDBMS
Support only non relational database
To interpret JavaScript code
If you have a function f and an object o, you can define a method named m of o with
o.m=m.f;
o.m=f;
o=f.m;
o=f;
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.unshift(1);
a.unshift(22);
a.shift();
a.unshift(3,[4,5]);
a.shift();
a.shift();
a.shift();
1
[4,5]
[3,4,5]
Exception is thrown
A function with no return value is called ___________
Procedures
Method
Static function
Dynamic function
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?
{
if (a == 1)
continue;
else
a++;
}
The continue keyword restarts the loop
The continue keyword skips the next iteration
The continue keyword skips the rest of the statements in that iteration
The continue keyword breaks out of the loop
To determine whether one object is the prototype of (or is part of the prototype chain of) another object, one should use the ____________
isPrototypeOf() method
equals() method
=== operator
==opertor
What happens in the following javaScript code snippet?
var count = 0;
while (count < 10)
{
console.log(count);
count++;
}
while (count < 10)
{
console.log(count);
count++;
}
The values of count are logged or stored in a particular location or storage
The value of count from 0 to 9 is displayed in the console
An error is displayed
An exception is thrown
What will be the output of the following Javascript code?
<script>
txt1 = “ one”;
txt1 += “two”;
document.getElementById("demo").innerHTML = txt1;
</script>
txt1 = “ one”;
txt1 += “two”;
document.getElementById("demo").innerHTML = txt1;
</script>
onetwo
one two
error
undefined
Which keyword is used to define the function in javascript?
void
int
function
main
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);
const obj2 = Object.freeze(obj1);
obj2.property1 = '20';
console.log(obj2.property1);
10
20
Runtime error
Compilation error
The enumeration order becomes implementation dependent and non-interoperable if ___________
If the object inherits enumerable properties
The object does not have the properties present in the integer array indices
The delete keyword is never used
Object.defineProperty() is not used
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;
w = x = y = z;
q = a?b:c?d:e?f:g;
x = ~(-y); w = (x = (y = z));
q = a?b:(c?d:(e?f:g));
x = a?b:(c?d:(e?f:g));
q = ~(-y); w = (x = (y = z));
x = (x = (y = z));w = ~(-y);
q = a?b:(c?d:(e?f:g));
x = ~(-y); w = (x = (y = z));
q = (c?d:(e?f:g));
What is the difference between the two lines given below ?
!!(obj1 && obj2);
(obj1 && obj2);
(obj1 && obj2);
Both the lines result in a boolean value True
Both the lines result in a boolean value False
Both the lines checks just for the existence of the object alone
The first line results in a real boolean value whereas the second line merely checks for the existence of the objects
A hexadecimal literal begins with __________
00
0x
0X
Both 0x and 0X
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>
var x = 5;
var y = 2;
var z = x % y;
document.getElementById("demo").innerHTML = z;
</script>
0
1
2
5
JavaScript _________ when there is an indefinite or an infinite value during an arithmetic computation.
Prints an exception error
Prints an overflow error
Displays Infinity
Prints the value as such
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);
}
var b = 0;
while (a < 3)
{
a++;
b += a;
console.log(b);
}
135
123
013
01
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?
{
var len = a.length, i = 0;
if (len == 0)
console.log(Empty Array);
else
{
do
{
console.log(a[i]);
} while (++i < len);
}
}
Prints the numbers in the array in order
Prints the numbers in the array in the reverse order
Prints 0 to the length of the array
Prints Empty Array
What will be the output of the following JavaScript code?
const object1 = {
property1: 20
};
console.log(Object.is(object1));
property1: 20
};
console.log(Object.is(object1));
20
true
false
error
A conditional expression is also called a _______________
Alternative to if-else
Immediate if
If-then-else statement
Switch statement
What will happen if reverse() and join() methods are used simultaneously?
Reverses and stores in the same array
Reverses and concatenates the elements of the array
Reverses
Stores the elements of an array in normal order
JavaScript can be written __________
directly into JS file and included into HTML
directly on the server page
directly into HTML pages
directly into the css file
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++;
}
{
document.writeln(num);
}
while(num>=1)
{
document.writeln(num);
num++;
}
Code 1
Code 2
Both Code 1 and Code 2
Cannot Compare
When an empty statement is encountered, a JavaScript interpreter __________
Ignores the statement
Prompts to complete the statement
Throws an error
Shows a warning
Do functions in JavaScript necessarily return a value?
It is mandatory
Not necessary
Few functions return values by default
some functions do not return any value
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;
}
{
for (; o.next; o = o.next) ;
return o;
}
No, this will throw an exception as only numerics can be used in a for loop
No, this will not iterate
Yes, this will work
No, this will result in a runtime error with the message Cannot use Linked List