Operators and Conditional Statements

Beginning of Chapter 2

• In Chapter 2 of the JavaScript series, we will focus on operators and conditional statements.
• All past and future chapters will be available in the channel's playlist.

Real-life Examples

• Example: Age requirement for voter ID and license.
• Condition of passing marks to pass a class.
• Similar conditions are implemented in code and websites.

Comments

• The part of the code in JavaScript that does not get executed.
• Useful for explaining the code.
• Single Line Comments: //
• Multiple Line Comments: /* ... */

Code Setup

• index.html: Basic HTML5 boilerplate code
• script.js: Script file
• Connecting script.js to HTML using the script tag
• Example: console.log('Hello World');

Arithmetic Operators

• Increment Operator: ++
• Decrement Operator: --

Operators

• Plus: +
• Minus: -
• Multiply: *
• Divide: /
• Modulus: % (to get the remainder)
• Exponentiation: ** (example: a ** b)

Unary Operators

• Increment: a++ <=> a = a + 1
• Decrement: a-- <=> a = a - 1

Assignment Operators

• = : Assigning a value to a variable
• **+=, -=, *=, /=, %=, **= **: Compound assignment operators

Illustrative Example

• a += 4 signifies a = a + 4

Comparison Operators

• Equal to: ==
• Not equal to: !=
• Strict equal to: ===
• Strict not equal to: !==
• Greater than: >
• Less than: <
• Greater than or equal to: >=
• Less than or equal to: <=

Logical Operators

• AND: &&
• OR: ||
• NOT: !

Conditional Statements

• Using conditional statements to implement some conditions in the code.

If Statement

• Checking a condition, if the statement is true the code block is executed.

  if (condition) {
      // Code to be executed if condition is truthy
  }
  

Else Statement

if (condition) {
    // Code to be executed if condition is truthy
} else {
    // Code to be executed if condition is falsy
}

Else If Statements

if (condition1) {
    // Code to execute if condition1 is true
} else if (condition2) {
    // Code to execute if condition2 is true
} else {
    // Code to execute if none of the above conditions are true
}

Ternary Operator

• Syntax: condition ? expr1 : expr2
• Example: let result = (age >= 18) ? 'Adult' : 'Not Adult';

MDN Documentation

• A good resource for reading programming documentation.

Larger Examples and Practice Questions

• Checking multiples of a number
• Student Grading System

Practice Questions

1. Take a number from the user and check whether it is a multiple of 3 or 5.
2. Assign a grade based on the student's score:
   • 90-100: A
   • 70-89: B
   • 60-69: C
   • 50-59: D
   • 0-49: F

Plan

1. Take input from the user via prompt
2. Check if-else conditions
3. Display the result at the end

Practice Code:

// Multiple Check
let number = prompt('Enter a number:');
if (number % 3 === 0) {
    console.log(number + ' is a multiple of 3');
} else if (number % 5 === 0) {
    console.log(number + ' is a multiple of 5');
} else {
    console.log(number + ' is not a multiple of 3 or 5');
}

// Grading System
let score = prompt('Enter your score:');
let grade;
if (score >= 90 && score <= 100) {
    grade = 'A';
} else if (score >= 70 && score <= 89) {
    grade = 'B';
} else if (score >= 60 && score <= 69) {
    grade = 'C';
} else if (score >= 50 && score <= 59) {
    grade = 'D';
} else if (score >= 0 and score <= 49) {
    grade = 'F';
}
console.log('According to your score, your grade is ' + grade);