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Operators and Expressions in JavaScript

Patricia Arquette

Release： 2024-12-14 21:49:15

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Operators and Expressions in JavaScript

Day 3: Operators and Expressions in JavaScript

Welcome to Day 3 of learning JavaScript! Today, we’ll explore operators and expressions—essential tools for performing calculations, making decisions, and writing meaningful logic in your programs.

What Are Operators?

Operators are special symbols or keywords that perform operations on values or variables. These operations can range from arithmetic calculations to logical decisions.

Types of Operators in JavaScript

1. Arithmetic Operators

Used for mathematical operations like addition, subtraction, multiplication, etc.

Operator	Description	Example	Output
	Addition	5 3	8
-	Subtraction	10 - 6	4
*	Multiplication	4 * 2	8
/	Division	12 / 4	3
%	Modulus (Remainder)	10 % 3	1
**	Exponentiation	2 ** 3	8

Operator

Description

Example

let num1 = 10;
let num2 = 3;
console.log(num1 + num2); // 13
console.log(num1 % num2); // 1

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Output

Addition

5 3

Subtraction

10 - 6

Multiplication

4 * 2

Division

12 / 4

Modulus (Remainder)

10 % 3

Exponentiation

2 ** 3

Example:

Operator	Description	Example	Output
==	Equal to	5 == "5"	true
===	Strict equal to	5 === "5"	false
!=	Not equal to	5 != "5"	false
!==	Strict not equal	5 !== "5"	true
<	Less than	5 < 10	true
>	Greater than	10 > 5	true
<=	Less than or equal	5 <= 5	true
>=	Greater than or equal	10 >= 5	true

2. Relational (Comparison) Operators Used to compare two values and return a Boolean (true or false).

Operator	Description	Example	Output
==	Equal to	5 == "5"	true
===	Strict equal to	5 === "5"	false
!=	Not equal to	5 != "5"	false
!==	Strict not equal	5 !== "5"	true
<	Less than	5 < 10	true
>	Greater than	10 > 5	true
<=	Less than or equal	5 <= 5	true
>=	Greater than or equal	10 >= 5	true

Example:

let num1 = 10;
let num2 = 3;
console.log(num1 + num2); // 13
console.log(num1 % num2); // 1

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3. Logical Operators

Combine multiple conditions or invert logic.

Operator	Description	Example	Output
&&	Logical AND	true && false	false
`		`	Logical OR
!	Logical NOT	!true	false

Operator

Description

Example

let age = 20;
console.log(age >= 18); // true
console.log(age === "20"); // false

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Output

Logical AND

true && false

false

Logical OR

Logical NOT

!true

false

Example:

Operator	Description	Example	Output
=	Assign	x = 10	10
=	Add and assign	x = 5	x = x 5
-=	Subtract and assign	x -= 3	x = x - 3
*=	Multiply and assign	x *= 2	x = x * 2
/=	Divide and assign	x /= 2	x = x / 2
%=	Modulus and assign	x %= 3	x = x % 3

4. Assignment Operators

Used to assign values to variables.

let isAdult = true;
let hasID = false;
console.log(isAdult && hasID); // false
console.log(isAdult || hasID); // true

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Operator	Description	Example	Output
=	Assign	x = 10	10
=	Add and assign	x = 5	x = x 5
-=	Subtract and assign	x -= 3	x = x - 3
*=	Multiply and assign	x *= 2	x = x * 2
/=	Divide and assign	x /= 2	x = x / 2
%=	Modulus and assign	x %= 3	x = x % 3

Example:

Operator	Description	Precedence
**	Exponentiation	1
*, /, %	Multiplication, Division, Modulus	2
, -	Addition, Subtraction	3
<, >, ==, !=	Comparison	4
&&	Logical AND	5
`		`

Expressions and Precedence An expression is a piece of code that produces a value. For example, 5 3 is an expression, and its value is 8. Operator Precedence When multiple operators are used, JavaScript decides the order of execution based on precedence. Operators with higher precedence are executed first.

Operator	Description	Precedence
**	Exponentiation	1
*, /, %	Multiplication, Division, Modulus	2
, -	Addition, Subtraction	3
<, >, ==, !=	Comparison	4
&&	Logical AND	5
`		`

Example of Precedence:

let num1 = 10;
let num2 = 3;
console.log(num1 + num2); // 13
console.log(num1 % num2); // 1

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Use parentheses () to control precedence.

let age = 20;
console.log(age >= 18); // true
console.log(age === "20"); // false

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Practice for Today

Write a program to calculate the area of a rectangle using arithmetic operators.
Compare two numbers using relational operators and log whether they are equal or one is greater.
Create a simple program to check if a person is eligible to vote using logical operators.

Summary of Day 3

Today, we covered:

Arithmetic Operators: For calculations.
Relational Operators: For comparisons.
Logical Operators: For combining conditions.
Assignment Operators: For assigning and updating values.
Expressions and Precedence: Understanding execution order.

Next Steps

In Day 4, we’ll learn about Control Flow in JavaScript, focusing on conditional statements and loops. Stay tuned for Dec 11, 2024!

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