JavaScript

Question 1

What is JavaScript

Answer 1

JavaScript is a text-based programming language used both on the client-side and server-side that allows you to make web pages interactive.

Question 2

How to open Developer Tools in Google Chrome ?

Answer 2

Keyboard Shortcut is :-

ctrl + shift + i

Question 3

How to open console in Google Chrome ?

Answer 3

KeyBoard Shortcut is :-

ctrl + shift + j

Question 4

Hot to write JS code from Google Chrome Console ?

Answer 4

Open Console window , & start typing JS code , hit enter to run code ?

Question 5

How to Use alert in JS ?

Answer 5

alert + brackets + message to display in double quotes

alert(“Java Script is Fun”)

Question 6

How to Declare variables in Java Script ?

Answer 6

We have 5 ways to Declare a Variable :-

1. let age = 25;
2. var countryName = ‘India’
3. const year = 1998;
4. let firstName; //undefined
5. lastName; // Dynamic Typing

Question 7

How to write if Condition in Java Script ?

Answer 7

if keyword + condition in brackets + action statements in curly braces

let a = 10;

if (a==10)    alert('Java Script is FUN! ');
      or 
if (a==10){
   alert('Java Script is FUN! ');
}

Question 8

How to write JS code inside a HTML Document ?

Answer 8

We have to use script element .

<
script>

<
/script>

Question 9

How to get connected with google console ?

Answer 9

We have to use console.log method .

console.log(4+5+6+7+8)

Question 10

How to load JavaScript file ?

Answer 10

We have to use script element under body of HTML Document .

<
script src=”script.js”><
/script>

Question 11

How to load JavaScript file ?

Answer 11

We have to use script element under body of HTML Document .

<
script src=”script.js”><
/script>

Question 12

What is an values in JavaScript ?

Answer 12

Value is an piece of Data.

It is the most fundamental unit of information in programing .

Question 13

What is an values in JavaScript ?

Answer 13

Value is an piece of Data.

It is the most fundamental unit of information in programing .

Question 14

How to Declare a variable in JavaScript ?

Answer 14

let fitstName= “Hemant”

Question 15

How to Declare a variable in JavaScript ?

Answer 15

let fitstName= “Hemant”

Question 16

How to pass an varaibale to Browser console ?

Answer 16

let firstName = "Hemant" ;
console.log(firstName) ;

Question 17

What you include in Variable name ,according to naming convention in JvaScript ?

Answer 17

The variable name only contains ,letters,numbers,undercore & dollar

Question 18

By which JavaScript variable starts with,according to conventions ?

Answer 18

JavaScript variables only starts with

lowercase letters,underscore or Dollar ?

Question 19

How many Data Types are in JavaScript ?

Answer 19

Two Types :-

Primitifve & Objects

Question 20

What are the Primitive Data Types in JavaScript ?

Answer 20

We have total Severn Data Types in JavaScript ?

1. Number - let age=23;
2. String - let firstName = “Hemant”;
3. Boolean - isMale = true
4. Undefined - let children;
5. Null
6. Symbol
7. BigInt

Question 21

What is dynamic typing in JavaScript ?

Answer 21

It means automatic detection of data type
We dont have to manually define the data type,data types are determined automatically by JavaSript when it detects the value.
firstName = “Hemant”
JS automatically consider this as string data type.

Question 22

How to know the type of value by chrome console ?

Answer 22

console. log(typeof true)

console. log(typeof javaScriptIsFun)

Question 23

How to Declare undefined variable ?

Answer 23

let year;

Question 24

What term is called when we resign a variable ?

Answer 24

reassigning a variable is called mutation of variable or variable is mutated.

Question 25

What is mutation in JavaScriptt

Answer 25

Re-Assighning a variable

Question 26

What is mutation in JavaScriptt

Answer 26

``` Re-Assighning a variable let age = 30; age = 31 ; ```

Question 27

How to Declare Constant in JavaScript ?

Answer 27

``` const birthYear = 1991; Here variable initialization is is mandatory ,without this JS gives error. ```

Question 28

What are immutable variables in JavasScript ?

Answer 28

``` Constant variables are immutable variables,whose value did not change in Program. const birthYear = 1990 ```

Question 29

What are mutable variables in JavaScript ?

Answer 29

``` Variables whose value is able to modified in program let age = 31, or we can say that varibles declared as , let age = 24; var gender = "M" firstName = "Hemant" //dynamic typing ```

Question 30

What if we dont assighn a value to constant variable while declaring

Answer 30

Console gives Syntax Error: Missing initializer in const declaration .

Question 31

What is Variable Mutation ?

Answer 31

Reassigning value to variable is called Variable Mutation.

Question 32

What is a Difference Between , declaring a variable with let & var ?

Answer 32

let variable cant redeclared | var variable canbe redeclared

Question 33

How many Operators are in JavaScript ?

Answer 33

We have 5 type of operators in JavaSscript 1. typeof operator 2. Math operator + - * / ** 3. Assighnment Operators. 4. comparison operator > < >= <= == 5. Logical Operators - && , || , !

Question 34

How to log multiple values to console ?

Answer 34

``` const ageSundy = 2022 - 1979 ; const agePinky = 2022 - 1985 ; console.log(ageSundy,agePinky) ```

Question 35

How to do calculation in console log ?

Answer 35

``` const ageHemsnt = 41; console.log(ageHemsnt*2,ageHemsnt/2,2 ** 3) ```

Question 36

How to write exponent in JavaScript ?

Answer 36

``` console.log(2 ** 3) // 2 raise to the power of three. ```

Question 37

How to concatenate two Strings ?

Answer 37

By using add math operator const firstName = "Hemant " const lastName = "Kumar" console.log(firstName+lastName)

Question 38

What do you mean by evaluation sequence of Operators ?

Answer 38

It is called Operator Precedence,means priority of evaluating the operators, which one is evaluated first https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence

Question 39

What is MDN

Answer 39

Mozilla Development Network

Question 40

How can we Concatenate string with variables ?

Answer 40

We may use add operator , but best way is to use Template Literals . ``` const firstName = "Hemant" const job = "IT Professional" const birthYear = 1979 const year = 2022 //Using Math Operator let hemant = "I'm " + firstName + ' a ' + (year - birthYear) + ' Year Old ' + job console.log(hemant) //Using Template literals let userDetails = `"I'm ${firstName} a ${year - birthYear} Year Old {$ job}` console.log(userDetails) ```

Question 41

What are Template Literals ?

Answer 41

``` Template Literal can assemble multiple pieces into one final string. const firstName = "Hemant" const job = "IT Professional" const birthYear = 1979 const year = 2022 console.log(hemant) const hemantNew = `I'm ${firstName}, a ${year - birthYear} year old ${job}` ```

Question 42

How to write strings with Template Literals ?

Answer 42

``` const str1 = `Just a Regular String ` console.log(str1) ```

Question 43

How to write multiline strings ?

Answer 43

const str1 = `String with Multiple Lines` console.log(str1)

Question 44

How to typecast to Number ?

Answer 44

We have to use Number() Function const inputYear= '1991'; console.log(Number(inputYear) + 18)

Question 45

What is NaN ?

Answer 45

It means Not an Number

Question 46

What is NaN ?

Answer 46

It means Not an Number

Question 47

How to type cast to String ?

Answer 47

``` We have to use string funnction . const age=23; console.log(typeof String(age)) ```

Question 48

What is type conversion & type coercion ?

Answer 48

Type Coercion is an implicit or automatic type conversion , JavaScript is doing automatically for us. Manual type casting is called Explicit type conversion

Question 49

What are falsy values and what they are ?

Answer 49

Values which considerd as boolean false is known as falsy values . ``` They are 5 falsy values :- 1, Zero, 0 2. empty string , "" 3. undefined 4.Null 5. NaN ``` Values other than this are True Values

Question 50

Give example of undefined variable ?

Answer 50

let height; if(height) console.log("Height is Defined") else console.log("Height is not Defined")

Question 51

What are Equality operators in JavaScript ?

Answer 51

We have 2 types of Equality Operators :- 1. Strict Equality Operator === no typeconversion 2. Loose Equality Operator == implicit type casting done by JavaScript

Question 52

How to get input from Browser ?

Answer 52

``` We have to use prompt() function. const favourite = prompt("What is your Favourite number : -") ```

Question 53

How to display variable in alert() Function ?

Answer 53

``` We have to use Template Literals in alert() Function :- const favourite = prompt("What is your Favourite number : -") alert(`Number Entered by you is ${favourite}`) ```

Question 54

What is Different Operator in JavaScript ?

Answer 54

Opposite of Equality operator is called Different Operator.They are of 2 types. 1. Loose Different Operator - != 2. Strict defferent operator - !==

Question 55

Give an Example of logical operators ?

Answer 55

``` const hasDrivingLicense = true; const hasGoodVision = true; const isTired = true; if (hasDrivingLicense && hasGoodVision || !isTired){ console.log('Sarah is able to drive') }else{ console.log('Someone else should Drive') } ```

Question 56

What is the term which converts one datype to other ?

Answer 56

``` The term is called typecasting, it is of two ,types :- 1. Implicit typecasting or type coercion - done automatically by JS firstName = "Hemant" + 22; // here number 22 is tycasted to string & assigned as string to variable firstName automatically by Java Script 2. Explicit typecasting - It is Manual typecasting, done by Developer itself let year = String(1991) // here number 1991 is typecast to string & assigned to variable year ```

Question 57

How to create Java Script File ?

Answer 57

We have to follow 3 Steps :- Step 1 : Open any text editor , Step 2: Create a New file, Step 3: Now save this file as script.js