JavaScript-Resource

Live Demo:- https://gmmamunh.github.io/JavaScript-Resource/

1. JavaScript Numbers
2. JavaScript Number Methods
3. JavaScript Strings

Primitive Data Types

JavaScript Numbers

Adding Numbers and Strings

WARNING !!

JavaScript uses the + operator for both addition and concatenation.

Numbers are added. Strings are concatenated.

let x = 10;
let y = 20;
let z = "30";
let result = x + y + z;

NB: The JavaScript interpreter works from left to right.

NaN - Not a Number

You can use the global JavaScript function isNaN() to find out if a value is a not a number:

let x = 100 / "Apple";
isNaN(x);

Infinity

Division by 0 (zero) also generates Infinity:

let x =  2 / 0;
let y = -2 / 0;

Infinity is a number: typeof Infinity returns number.

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JavaScript Number Methods

These number methods can be used on all JavaScript numbers:

toString() toFixed()

The toString() Method

let x = 123;
x.toString();
(123).toString();
(100 + 23).toString();

By default, JavaScript displays numbers as base 10 decimals.

But you can use the toString() method to output numbers from base 2 to base 36.

Hexadecimal is base 16. Decimal is base 10. Octal is base 8. Binary is base 2.

let myNumber = 32;
myNumber.toString(32);
myNumber.toString(16);
myNumber.toString(12);
myNumber.toString(10);
myNumber.toString(8);
myNumber.toString(2);

The toFixed() Method

let x = 9.656;
x.toFixed(0);
x.toFixed(2);
x.toFixed(4);
x.toFixed(6);

Converting Variables to Numbers

There are 3 JavaScript methods that can be used to convert a variable to a number:

• Number()
• parseFloat()
• parseInt()

The Number() Method

 Number(true); // 1
 Number(false); // 0
 Number("10"); // 10
 Number("  10"); // 10
 Number("10  "); // 10
 Number(" 10  "); // 10
 Number("10.33"); // 10.33
 Number("10,33"); // NaN
 Number("10 33"); // NaN
 Number("John"); // NaN

If the number cannot be converted, NaN (Not a Number) is returned.

The parseInt() Method

The parseInt() parses a string and returns a whole number. Spaces are allowed. Only the first number is returned:

 parseInt("-10"); // -10
 parseInt("-10.33"); // -10
 parseInt("10"); // 10
 parseInt("10.33"); // 10
 parseInt("10 20 30"); // 10
 parseInt("10 years"); // 10
 parseInt("years 10"); // NaN

If the number cannot be converted, NaN (Not a Number) is returned.

The parseFloat() Method

parseFloat() parses a string and returns a number. Spaces are allowed. Only the first number is returned:

parseFloat("10"); //10
parseFloat("10.33"); // 10.33
parseFloat("10 20 30"); // 10
parseFloat("10 years"); // 10
parseFloat("years 10"); // NaN

JavaScript Strings

You can use quotes inside a string, as long as they don't match the quotes surrounding the string:

let answer1 = "It's alright";
let answer2 = "He is called 'Johnny'";
let answer3 = 'He is called "Johnny"';

String Length

To find the length of a string, use the built-in length property:

let text = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
let length = text.length;

Escape Character

Because strings must be written within quotes, JavaScript will misunderstand this string:

let text = "We are the so-called "Vikings" from the north.";

The string will be chopped to "We are the so-called ".

The solution to avoid this problem, is to use the backslash escape character.

The backslash (\) escape character turns special characters into string characters:

Code	Result	Description
'	'	Single quote
"	"	Double quote
\	\	Backslash

The sequence " inserts a double quote in a string:

let text = "We are the so-called \"Vikings\" from the north.";

The sequence ' inserts a single quote in a string:

let text= 'It\'s alright.';

The sequence \ inserts a backslash in a string:

let text = "The character \\ is called backslash.";

String Methods

JavaScript String concat()

concat() joins two or more strings:

let text1 = "Hello";
let text2 = "World";
let text3 = text1.concat(" ", text2);

// They both are same
let result1 = "Hello" + " " + "World!";
let result2 = "Hello".concat(" ", "World!");

JavaScript Operators

What is an Operator?

In JavaScript, an operator is a special symbol used to perform operations on operands (values and variables). For example,

2 + 3; // 5

Here + is an operator that performs addition, and 2 and 3 are operands.

JavaScript Operator Types

Here is a list of different operators you will learn in this tutorial.

• Arithmetic Operators
• Assignment Operators
• Comparison Operators
• Logical Operators
• String Operators

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JavaScript Arithmetic Operators

Arithmetic operators are used to perform arithmetic calculations. For example,

const number1 = 3 + 5; // 8
const number2 = 30 + 50; // 80

Here, the + operator is used to add two operands.

Operator	Name	Example
+	Addition	x + y
-	Subtraction	x - y
\*	Multiplication	x \* y
/	Division	x / y
%	Remainder	x % y
++	Increment (increments by 1)	++x or x++
--	Decrement (decrements by 1)	--x or x--

Example 1: Arithmetic operators in JavaScript

let x = 5;
let y = 3;

// addition
console.log('x + y = ', x + y);  // 8

// subtraction
console.log('x - y = ', x - y);  // 2

// multiplication
console.log('x * y = ', x * y);  // 15

// division
console.log('x / y = ', x / y);  // 1.6666666666666667

// remainder
console.log('x % y = ', x % y);   // 2

// increment
console.log('++x = ', ++x); // x is now 6
console.log('x++ = ', x++); // prints 6 and then increased to 7
console.log('x = ', x);     // 7

// decrement
console.log('--x = ', --x); // x is now 6
console.log('x-- = ', x--); // prints 6 and then decreased to 5
console.log('x = ', x);     // 5

JavaScript Assignment Operators

Assignment operators are used to assign values to variables. For example,

const num1 = 5;

Here, the = operator is used to assign value 5 to variable num1.

more below 👇🏻👇🏻

// Assign the value 50 to x
let x = 50;
// Assign the value 2 to y
let y = 2;
// Assign the value x + y to z:
let z = x + y;

Here's a list of commonly used assignment operators:

Operator	Name	Example
=	Assignment operator	a = 7; // 7
+=	Addition assignment	a += 5; // a = a + 5
-=	Subtraction Assignment	a -= 2; // a = a - 2
*=	Multiplication Assignment	a *= 3; // a = a * 3
/=	Division Assignment	a /= 2; // a = a / 2
%=	Remainder Assignment	a %= 2; // a = a % 2

Note: The commonly used assignment operator is =. You will understand other assignment operators such as +=, -=, *= etc. once we learn arithmetic operators.

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Operators in JavaScript

Types of JavaScript Operators

There are different types of JavaScript operators:

• Arithmetic Operators
• Assignment Operators
• Comparison Operators
• Logical Operators

JavaScript Arithmetic Operators:

Arithmetic Operators are used to perform arithmetic on numbers:

Arithmetic Operators Example

let a = 3;
let x = (100 + 50) * a;

Operator	Description
+	Addition
-	Subtraction
*	Multiplication
/	Division
%	Modulus (Division Remainder)

JavaScript Assignment Operators

Assignment operators assign values to JavaScript variables.

The Addition Assignment Operator (+=) adds a value to a variable.

Assignment

let x = 10;
x += 5;

Operator	Example	Same As
=	x = y	x = y
+=	x += y	x = x + y
-=	x -= y	x = x - y
*=	x *= y	x = x * y
/=	x /= y	x = x / y
%=	x %= y	x = x % y

JavaScript Comparison Operators

Note

Comparison operators compare two values and return a boolean value, either true or false

Operator	Description
==	Equal to
===	Equal value and equal type
!=	Not equal
!==	Not equal value or not equal type
>	Greater than
<	Less than
>=	Greater than or equal to
<=	Less than or equal to

Equal to (==)

Example

const a = 10;
const b = 20;

console.log(a == b);
console.log(50 == 50);
console.log("50" == 50);
console.log('A' == 'A');
console.log('Hello' == 'Hello');
console.log('Hello' == 'hello');
console.log('Hello' == 'world');

Equal value and equal type / strict equal operator (==)

Example

const a = 10;
const b = 20;

console.log(a === b);
console.log(50 === 50);
console.log("50" === 50);
console.log('A' === 'A');
console.log('Hello' === 'Hello');
console.log('Hello' === 'hello');
console.log('Hello' === 'world');

Not equal operator (!=)

Example

console.log(3 != 2); // true
console.log('hello' != 'Hello'); // true
console.log(5 != 5); // false

Not equal operator (!=)

Example

console.log(2 !== '2'); // true
console.log(2 !== 2); // false

JavaScript Unary Operators:

Operator	Description
++	increment
--	deincrement

JavaScript Logical Operators:

Operator	Description
&&	logical AND
||	logical OR
!	logical NOT

123456789

> <

const a = 10;
const b = 20;

> Greater than:-

console.log(10 > 20);
console.log(a > b);
console.log(50 > 49);

< Less than:-

console.log(10 < 20);
console.log(a < b);
console.log(60 < 50);

>= Greater than or Equal:-

console.log(10 > 10);

const age = 17;
console.log(age >= 18);

<= Less than or Equal

const age2 = 45;
console.log(age2 <= 45);

Problems Solve;

const personAge = 18;
console.log('Condition = ', personAge >= 18);

if (personAge >= 18) {
  console.log('Yes. Tumi Vote Dite Parba. 🏆');
}
if (personAge < 18) {
  console.log('No. Tumi Vote Dite Parba Na. 😭');
}

// =======>
let num1 = 10;
num1 = num1 + 1;
console.log(num1);
console.log(num1 + 1);

======================================

Unary Operatoers

1. Increment

A. Pre Increment => (++num)

B. Post Increment => (num++)

2. Decrement

A. Pre Decrement => (--num)

B. Post Decrement => (num--)

======================================

Pre Increment => (++num)

let num = 5;

console.log(++num);
console.log(++num);
console.log(num);
console.log(num);
console.log(num);

Post Increment => (num++)

console.log(num + 1);
console.log(num++);
console.log(num++);
console.log(num);

Pre Decrement => (--num)

let num = 5;

console.log(--num);
console.log(--num);
console.log(--num);

Post Decrement => (num--)

console.log(num--); console.log(num--); console.log(num--); console.log(--num);

# JavaScript Logical Operators:
## 1. && - (AND)
## 2. || - (OR)
## 3. ! - (NOT)

## && - (AND)
```js
console.log(10 == 10 && 40 > 10); // true
console.log(10 == 10 && 4 > 10); // false
console.log(10 == 11 && 40 > 10); // false
console.log(10 == 11 && 4 > 10); // false

|| - (OR)

console.log(10 == 10 || 40 > 10); // true
console.log(10 == 10 || 4 > 10); // true
console.log(10 == 11 || 40 > 10); // true
console.log(10 == 11 || 4 > 10); // false

! - (NOT)

const isAdult = true;
console.log(!isAdult);
console.log(!true);

AND (&&)

A - AND - B - Result

true && true = true

true && false = false

false && true = false

false && true = false

OR (||)

A - OR - B - Result

true || true = true

true || false = true

false || true = true

false || true = false

NOT (!)

true = false

false = true