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All questions of Introduction to JS for Software Development Exam
How do you comment a single line of code in JavaScript?- a)// This is a comment
- b)<!-- This is a comment -->
- c)/* This is a comment */
- d)// This is a comment //
Correct answer is option 'A'. Can you explain this answer?
How do you comment a single line of code in JavaScript?
a)
// This is a comment
b)
<!-- This is a comment -->
c)
/* This is a comment */
d)
// This is a comment //
|
Code Nation answered |
Single-line comments in JavaScript are denoted by //.
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Which of the following is a valid JavaScript data type?- a)Date
- b)Array
- c)String
- d)All of the above
Correct answer is option 'D'. Can you explain this answer?
Which of the following is a valid JavaScript data type?
a)
Date
b)
Array
c)
String
d)
All of the above
|
Ritesh Kumar Shivhare answered |
JavaScript supports multiple data types, including Date, Array, and String, among others.
What is the output of the following JavaScript code?
var x = 5;
console.log(x++);- a)5
- b)6
- c)Error
- d)Undefined
Correct answer is option 'A'. Can you explain this answer?
What is the output of the following JavaScript code?
var x = 5;
console.log(x++);
var x = 5;
console.log(x++);
a)
5
b)
6
c)
Error
d)
Undefined
|
|
Ritesh Kumar Shivhare answered |
The post-increment operator (x++) returns the current value of x (5) and then increments it to 6.
Which of the following is true about JavaScript?- a)It is a server-side scripting language.
- b)It can only be used for client-side scripting.
- c)It is a compiled language.
- d)e. b. It can only be used for client-side scripting. c. It is a compiled language.
Correct answer is option 'D'. Can you explain this answer?
Which of the following is true about JavaScript?
a)
It is a server-side scripting language.
b)
It can only be used for client-side scripting.
c)
It is a compiled language.
d)
e. b. It can only be used for client-side scripting. c. It is a compiled language.
|
|
Ritesh Kumar Shivhare answered |
JavaScript is an object-oriented programming language commonly used for client-side scripting in web development.
What is the output of the following JavaScript code?
function multiply(a, b) {
return a * b;
}var result = multiply(2, 3);
console.log(result);- a)2
- b)3
- c)6
- d)Error
Correct answer is option 'C'. Can you explain this answer?
What is the output of the following JavaScript code?
function multiply(a, b) {
return a * b;
}
return a * b;
}
var result = multiply(2, 3);
console.log(result);
console.log(result);
a)
2
b)
3
c)
6
d)
Error
|
Tanuj Arora answered |
The multiply() function takes two arguments and returns their product. The function is called with arguments 2 and 3, resulting in a return value of 6.
What is the output of the following JavaScript code?
var x = [1, 2, 3];
x.push(4);
console.log(x.length);- a)1
- b)2
- c)3
- d)4
Correct answer is option 'D'. Can you explain this answer?
What is the output of the following JavaScript code?
var x = [1, 2, 3];
x.push(4);
console.log(x.length);
var x = [1, 2, 3];
x.push(4);
console.log(x.length);
a)
1
b)
2
c)
3
d)
4
|
|
Tanuj Arora answered |
The push() method is used to add elements to the end of an array. In this case, it adds the number 4 to the array, resulting in a length of 4.
What is the output of the following JavaScript code?
function greet(name) {
console.log("Hello, " + name + "!");
}greet("John", "Doe");- a)Hello, John!
- b)Hello, Doe!
- c)Hello, John Doe!
- d)Error
Correct answer is option 'A'. Can you explain this answer?
What is the output of the following JavaScript code?
function greet(name) {
console.log("Hello, " + name + "!");
}
console.log("Hello, " + name + "!");
}
greet("John", "Doe");
a)
Hello, John!
b)
Hello, Doe!
c)
Hello, John Doe!
d)
Error
|
Tushar Shah answered |
The code provided is incomplete. In order to determine the output, the missing part of the code needs to be provided.
What will be the output of the following code snippet?
let x = 1;
{
let x = 2;
{
console.log(x);
let x = 3;
}
}- a)1
- b)2
- c)3
- d)ReferenceError
Correct answer is option 'D'. Can you explain this answer?
What will be the output of the following code snippet?
let x = 1;
{
let x = 2;
{
console.log(x);
let x = 3;
}
}
let x = 1;
{
let x = 2;
{
console.log(x);
let x = 3;
}
}
a)
1
b)
2
c)
3
d)
ReferenceError
|
KnowIT answered |
The 'console.log(x)' line tries to access 'x' before it is declared inside the inner block. Since 'let' has block scope, the declaration of 'x' inside the inner block shadows the outer 'x' variable, and it is not accessible before its declaration.
What will be the output of the following code snippet?
console.log(typeof NaN === "number");- a)true
- b)false
- c)NaN
- d)undefined
Correct answer is option 'A'. Can you explain this answer?
What will be the output of the following code snippet?
console.log(typeof NaN === "number");
console.log(typeof NaN === "number");
a)
true
b)
false
c)
NaN
d)
undefined
|
|
Ritesh Kumar Shivhare answered |
The 'typeof' operator returns "number" for NaN (Not-a-Number) because NaN is a special numeric value in JavaScript.
What is the output of the following JavaScript code?
var x = 10;
var y = 5;
console.log(x += y);- a)10
- b)15
- c)5
- d)Error
Correct answer is option 'B'. Can you explain this answer?
What is the output of the following JavaScript code?
var x = 10;
var y = 5;
console.log(x += y);
var x = 10;
var y = 5;
console.log(x += y);
a)
10
b)
15
c)
5
d)
Error
|
|
Tanuj Arora answered |
The += operator is used for addition and assignment. It adds the value of y to x and assigns the result back to x, resulting in x being 15.
What will be the output of the following code snippet?
let x = 5;
(function() {
console.log(x);
let x = 10;
})();- a)5
- b)10
- c)undefined
- d)ReferenceError
Correct answer is option 'D'. Can you explain this answer?
What will be the output of the following code snippet?
let x = 5;
(function() {
console.log(x);
let x = 10;
})();
let x = 5;
(function() {
console.log(x);
let x = 10;
})();
a)
5
b)
10
c)
undefined
d)
ReferenceError
|
|
KnowIT answered |
The variable 'x' is declared using 'let' inside the immediately-invoked function expression (IIFE). Since 'let' has block scope, the declaration of 'x' inside the function creates a new variable that is not accessible before the declaration.
What will be the output of the following code snippet?
let x = 1;
function foo() {
console.log(x);
let x = 2;
}
foo();- a)1
- b)2
- c)undefined
- d)ReferenceError
Correct answer is option 'D'. Can you explain this answer?
What will be the output of the following code snippet?
let x = 1;
function foo() {
console.log(x);
let x = 2;
}
foo();
let x = 1;
function foo() {
console.log(x);
let x = 2;
}
foo();
a)
1
b)
2
c)
undefined
d)
ReferenceError
|
Anshika Chauhan answered |
Explanation:
The code snippet provided defines a variable `x` with the value of 1 and a function `foo`. When `foo` is called, it attempts to log the value of `x` to the console and then defines a new variable `x` with the value of 2.
Variable Hoisting:
In JavaScript, variable declarations using the `let` keyword are hoisted to the top of their scope, but they are not initialized. This means that the variable `x` is hoisted to the top of the `foo` function, but its value is not set until the line where it is defined.
Execution:
When the code is executed, the following steps occur:
1. The variable `x` is declared and initialized with the value of 1.
2. The `foo` function is defined.
3. The `foo` function is called.
4. Inside the `foo` function, the `console.log(x)` statement is executed.
- At this point, the variable `x` is hoisted to the top of the `foo` function, but its value is not set yet.
- Since the value of `x` is not set, it is undefined.
- Therefore, trying to log the value of `x` to the console will result in the output of `undefined`.
5. The variable `x` is defined with the value of 2.
- This line is never reached because the `console.log(x)` statement causes an error.
Error:
The error thrown is a ReferenceError because the variable `x` is referenced before it has been initialized with a value. This error occurs because the `let` keyword does not allow hoisting to the top of the scope, unlike the `var` keyword.
Therefore, the correct answer is option 'D) ReferenceError'.
The code snippet provided defines a variable `x` with the value of 1 and a function `foo`. When `foo` is called, it attempts to log the value of `x` to the console and then defines a new variable `x` with the value of 2.
Variable Hoisting:
In JavaScript, variable declarations using the `let` keyword are hoisted to the top of their scope, but they are not initialized. This means that the variable `x` is hoisted to the top of the `foo` function, but its value is not set until the line where it is defined.
Execution:
When the code is executed, the following steps occur:
1. The variable `x` is declared and initialized with the value of 1.
2. The `foo` function is defined.
3. The `foo` function is called.
4. Inside the `foo` function, the `console.log(x)` statement is executed.
- At this point, the variable `x` is hoisted to the top of the `foo` function, but its value is not set yet.
- Since the value of `x` is not set, it is undefined.
- Therefore, trying to log the value of `x` to the console will result in the output of `undefined`.
5. The variable `x` is defined with the value of 2.
- This line is never reached because the `console.log(x)` statement causes an error.
Error:
The error thrown is a ReferenceError because the variable `x` is referenced before it has been initialized with a value. This error occurs because the `let` keyword does not allow hoisting to the top of the scope, unlike the `var` keyword.
Therefore, the correct answer is option 'D) ReferenceError'.
What is the output of the following JavaScript code?
var x = 10;
if (x === "10") {
console.log("Equal");
} else {
console.log("Not equal");
}- a)Equal
- b)Not equal
- c)Error
- d)Undefined
Correct answer is option 'B'. Can you explain this answer?
What is the output of the following JavaScript code?
var x = 10;
if (x === "10") {
console.log("Equal");
} else {
console.log("Not equal");
}
var x = 10;
if (x === "10") {
console.log("Equal");
} else {
console.log("Not equal");
}
a)
Equal
b)
Not equal
c)
Error
d)
Undefined
|
|
Tanuj Arora answered |
The strict equality operator (===) compares both the value and the type. Since x is a number and "10" is a string, they are not equal.
Which of the following is NOT a valid data type in JavaScript?- a)String
- b)Boolean
- c)Number
- d)Character
Correct answer is option 'D'. Can you explain this answer?
Which of the following is NOT a valid data type in JavaScript?
a)
String
b)
Boolean
c)
Number
d)
Character
|
Neeraj Singh Kushwah answered |
JavaScript does not have a dedicated "Character" data type. Characters are represented as strings of length 1.
What will be the output of the following code snippet?
console.log(2 + "2");- a)22
- b)4
- c)2 + "2"
- d)2
Correct answer is option 'A'. Can you explain this answer?
What will be the output of the following code snippet?
console.log(2 + "2");
console.log(2 + "2");
a)
22
b)
4
c)
2 + "2"
d)
2
|
Startup Central Classes answered |
The + operator, when one operand is a string, performs string concatenation. Therefore, "2" is treated as a string, and the result is "22".
What will be the output of the following code snippet?
let x = 10;
{
console.log(x);
let x = 20;
}- a)10
- b)20
- c)undefined
- d)ReferenceError
Correct answer is option 'D'. Can you explain this answer?
What will be the output of the following code snippet?
let x = 10;
{
console.log(x);
let x = 20;
}
let x = 10;
{
console.log(x);
let x = 20;
}
a)
10
b)
20
c)
undefined
d)
ReferenceError
|
Hridoy Ghoshal answered |
Explanation:
Variable Scope:
- When a variable is declared using the `let` keyword, it is block-scoped.
- In the given code snippet, there is a variable `x` declared outside the block and another `x` declared inside the block.
Hoisting:
- Variables declared with `let` are hoisted to the top of their block but are not initialized.
- In the code snippet, the variable `x` inside the block is hoisted to the top of the block but not initialized.
Output:
- When the `console.log(x)` statement is executed, it refers to the `x` variable declared inside the block which is not initialized yet.
- This results in a `ReferenceError` because the `x` variable inside the block is in the temporal dead zone until it is initialized.
Therefore, the output of the given code snippet will be a ReferenceError.
How do you output a message to the console in JavaScript?- a)console.log()
- b)print()
- c)log()
- d)e.log() b. print() c. log()
Correct answer is option 'A'. Can you explain this answer?
How do you output a message to the console in JavaScript?
a)
console.log()
b)
print()
c)
log()
d)
e.log() b. print() c. log()
|
|
Nilotpal Jain answered |
Explanation:
console.log() function:
- In JavaScript, the console.log() function is used to output a message to the console.
- It is a built-in function that is commonly used for debugging purposes, displaying variables, or general logging.
- The console.log() function takes one or more arguments, which can be strings, numbers, objects, or other data types.
Usage:
- To use the console.log() function, simply write console.log() followed by the message you want to output in parentheses.
- For example, console.log("Hello, World!"); will output "Hello, World!" to the console.
Benefits:
- The console.log() function is a powerful tool for developers to quickly check the output of their code and track the flow of their program.
- It helps in identifying errors, debugging issues, and understanding the behavior of the code during runtime.
Example:
javascript
console.log("Hello, World!");
Conclusion:
- In JavaScript, the console.log() function is the standard way to output messages to the console and is an essential tool for developers to effectively debug and monitor their code.
console.log() function:
- In JavaScript, the console.log() function is used to output a message to the console.
- It is a built-in function that is commonly used for debugging purposes, displaying variables, or general logging.
- The console.log() function takes one or more arguments, which can be strings, numbers, objects, or other data types.
Usage:
- To use the console.log() function, simply write console.log() followed by the message you want to output in parentheses.
- For example, console.log("Hello, World!"); will output "Hello, World!" to the console.
Benefits:
- The console.log() function is a powerful tool for developers to quickly check the output of their code and track the flow of their program.
- It helps in identifying errors, debugging issues, and understanding the behavior of the code during runtime.
Example:
javascript
console.log("Hello, World!");
Conclusion:
- In JavaScript, the console.log() function is the standard way to output messages to the console and is an essential tool for developers to effectively debug and monitor their code.
What is the output of the following JavaScript code?
var x = 5;function update() {
x = 10;
}update();
console.log(x);- a)5
- b)10
- c)Error
- d)Undefined
Correct answer is option 'B'. Can you explain this answer?
What is the output of the following JavaScript code?
var x = 5;
function update() {
x = 10;
}
x = 10;
}
update();
console.log(x);
console.log(x);
a)
5
b)
10
c)
Error
d)
Undefined
|
|
Tanuj Arora answered |
The update() function modifies the global variable x by assigning it a new value of 10. The console.log() statement outputs the updated value.
What will be the output of the following code snippet?
var x = 10;
function foo() {
console.log(x);
var x = 20;
}
foo();- a)10
- b)20
- c)undefined
- d)ReferenceError
Correct answer is option 'C'. Can you explain this answer?
What will be the output of the following code snippet?
var x = 10;
function foo() {
console.log(x);
var x = 20;
}
foo();
var x = 10;
function foo() {
console.log(x);
var x = 20;
}
foo();
a)
10
b)
20
c)
undefined
d)
ReferenceError
|
Qudrat Chauhan answered |
Variable hoisting causes the declaration of 'var x' inside the function to be hoisted to the top. However, it is initialized with the value 'undefined' before the assignment. Therefore, the output is 'undefined'.
What will be the output of the following code snippet?
for (let i = 0; i < 3; i++) {
setTimeout(function() {
console.log(i);
}, 1000);
}- a)0, 1, 2
- b)3, 3, 3
- c)1, 2, 3
- d)0, 0, 0
Correct answer is option 'D'. Can you explain this answer?
What will be the output of the following code snippet?
for (let i = 0; i < 3; i++) {
setTimeout(function() {
console.log(i);
}, 1000);
}
for (let i = 0; i < 3; i++) {
setTimeout(function() {
console.log(i);
}, 1000);
}
a)
0, 1, 2
b)
3, 3, 3
c)
1, 2, 3
d)
0, 0, 0
|
|
Qudrat Chauhan answered |
The 'setTimeout' function is asynchronous. By the time the 'console.log(i)' is executed, the loop has already completed, and the value of 'i' is 3. Therefore, the output is 0, 1, 2.
What is the output of the following JavaScript code?
var x = 10;
var y = "5";
console.log(x + y);- a)15
- b)105
- c)"105"
- d)Error
Correct answer is option 'C'. Can you explain this answer?
What is the output of the following JavaScript code?
var x = 10;
var y = "5";
console.log(x + y);
var x = 10;
var y = "5";
console.log(x + y);
a)
15
b)
105
c)
"105"
d)
Error
|
|
Ritesh Kumar Shivhare answered |
JavaScript performs type coercion and converts the number 10 to a string before concatenating it with the string "5".
What will be the output of the following code snippet?
var x = 10;
function foo() {
console.log(x);
if (false) {
var x = 20;
}
}
foo();- a)10
- b)20
- c)undefined
- d)ReferenceError
Correct answer is option 'A'. Can you explain this answer?
What will be the output of the following code snippet?
var x = 10;
function foo() {
console.log(x);
if (false) {
var x = 20;
}
}
foo();
var x = 10;
function foo() {
console.log(x);
if (false) {
var x = 20;
}
}
foo();
a)
10
b)
20
c)
undefined
d)
ReferenceError
|
|
Anshika Chauhan answered |
Explanation:
The output of the code snippet will be 10.
Code Explanation:
1. The variable x is declared and assigned a value of 10.
2. The function foo() is defined, which logs the value of x to the console.
3. Inside the function, there is an if statement with a condition of false.
4. Inside the if statement, a new variable x is declared and assigned a value of 20.
5. Since the condition of the if statement is false, the code inside the if statement is not executed.
6. The function foo() is called, which logs the value of x to the console.
7. As there is no variable x declared inside the function foo(), it uses the variable x declared in the outer scope.
8. Thus, the value of x is 10 and it is logged to the console.
Key Points:
- The variable x is hoisted to the top of the function scope.
- Hoisting is a JavaScript behavior where variable and function declarations are moved to the top of their containing scope before code execution.
- Since the variable x is hoisted, the code inside the if statement is actually interpreted as:
```
var x;
if (false) {
x = 20;
}
```
- As the if statement is never executed, the value of x remains unchanged as 10.
- Therefore, when the function foo() is called, it logs the value of x as 10.
The output of the code snippet will be 10.
Code Explanation:
1. The variable x is declared and assigned a value of 10.
2. The function foo() is defined, which logs the value of x to the console.
3. Inside the function, there is an if statement with a condition of false.
4. Inside the if statement, a new variable x is declared and assigned a value of 20.
5. Since the condition of the if statement is false, the code inside the if statement is not executed.
6. The function foo() is called, which logs the value of x to the console.
7. As there is no variable x declared inside the function foo(), it uses the variable x declared in the outer scope.
8. Thus, the value of x is 10 and it is logged to the console.
Key Points:
- The variable x is hoisted to the top of the function scope.
- Hoisting is a JavaScript behavior where variable and function declarations are moved to the top of their containing scope before code execution.
- Since the variable x is hoisted, the code inside the if statement is actually interpreted as:
```
var x;
if (false) {
x = 20;
}
```
- As the if statement is never executed, the value of x remains unchanged as 10.
- Therefore, when the function foo() is called, it logs the value of x as 10.
What is the output of the following JavaScript code?
var x = 5;function increment() {
var x = 10;
x++;
}increment();
console.log(x);- a)5
- b)10
- c)11
- d)Error
Correct answer is option 'A'. Can you explain this answer?
What is the output of the following JavaScript code?
var x = 5;
function increment() {
var x = 10;
x++;
}
var x = 10;
x++;
}
increment();
console.log(x);
console.log(x);
a)
5
b)
10
c)
11
d)
Error
|
|
Tanuj Arora answered |
The variable x inside the increment() function is a separate variable from the global x. Modifying the local x doesn't affect the global x.
What is the purpose of a JavaScript function?- a)To declare variables
- b)To perform mathematical operations
- c)To store data
- d)To organize and reuse code
Correct answer is option 'D'. Can you explain this answer?
What is the purpose of a JavaScript function?
a)
To declare variables
b)
To perform mathematical operations
c)
To store data
d)
To organize and reuse code
|
|
Neeraj Singh Kushwah answered |
Functions in JavaScript allow for code organization and reusability by encapsulating a set of instructions.
What is JavaScript?- a)A markup language
- b)A programming language
- c)A database management system
- d)A communication protocol
Correct answer is option 'B'. Can you explain this answer?
What is JavaScript?
a)
A markup language
b)
A programming language
c)
A database management system
d)
A communication protocol
|
Coders Trust answered |
JavaScript is a high-level, interpreted programming language primarily used for web development.
What is the output of the following JavaScript code?
var x = "Hello";
console.log(x.length);- a)5
- b)6
- c)1
- d)Error
Correct answer is option 'A'. Can you explain this answer?
What is the output of the following JavaScript code?
var x = "Hello";
console.log(x.length);
var x = "Hello";
console.log(x.length);
a)
5
b)
6
c)
1
d)
Error
|
|
Tanuj Arora answered |
The length property is used to determine the number of characters in a string. In this case, the string "Hello" has a length of 5.
What will be the output of the following code snippet?
console.log("2" - 1);- a)1
- b)2
- c)"2" - 1
- d)"2" - "1"
Correct answer is option 'A'. Can you explain this answer?
What will be the output of the following code snippet?
console.log("2" - 1);
console.log("2" - 1);
a)
1
b)
2
c)
"2" - 1
d)
"2" - "1"
|
|
Startup Central Classes answered |
The - operator performs arithmetic subtraction. In this case, the string "2" is converted to the number 2, and the result is 2 - 1 = 1.
What is the purpose of JavaScript comments?- a)To make the code more readable and maintainable.
- b)To disable certain parts of the code temporarily.
- c)To specify the version of JavaScript use
- d)e. b. To disable certain parts of the code temporarily. c. To specify the version of JavaScript use
Correct answer is option 'A'. Can you explain this answer?
What is the purpose of JavaScript comments?
a)
To make the code more readable and maintainable.
b)
To disable certain parts of the code temporarily.
c)
To specify the version of JavaScript use
d)
e. b. To disable certain parts of the code temporarily. c. To specify the version of JavaScript use
|
|
Ritesh Kumar Shivhare answered |
JavaScript comments are used to add explanatory notes to the code, making it easier to understand and maintain.
What is the output of the following JavaScript code?
var x = 5;function multiplyByTwo(x) {
return x * 2;
}var result = multiplyByTwo(x);
console.log(result);- a)5
- b)10
- c)15
- d)Error
Correct answer is option 'A'. Can you explain this answer?
What is the output of the following JavaScript code?
var x = 5;
function multiplyByTwo(x) {
return x * 2;
}
return x * 2;
}
var result = multiplyByTwo(x);
console.log(result);
console.log(result);
a)
5
b)
10
c)
15
d)
Error
|
|
Coders Trust answered |
The multiplyByTwo() function has a local variable x, which shadows the global x. The local x is multiplied by 2, resulting in a return value of 10.
Which of the following is an example of a JavaScript framework?- a)Angular
- b)Django
- c)Ruby on Rails
- d)Flask
Correct answer is option 'A'. Can you explain this answer?
Which of the following is an example of a JavaScript framework?
a)
Angular
b)
Django
c)
Ruby on Rails
d)
Flask
|
|
Code Nation answered |
Angular is a popular JavaScript framework for building web applications.
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JavaScript for Web Development
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