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JavaScript if, else if, and switch Statements

⚙️ JavaScript if, else if, and switch Statements

? Quick Overview

JavaScript provides ways to control how your program runs using conditions: if, if else, else if, and switch. They allow your code to make decisions based on values and expressions.

? Key Concepts

  • if – runs code only when a condition is true.
  • if else – chooses between two outcomes.
  • else if – checks multiple conditions in order.
  • switch – compares one value to many cases.
  • Conditions – return true or false.
  • Blocks – code inside { } executes together.

? Syntax and Flow

? if Statement

? View Code Example 
// Check voting eligibility
let age = 18;
if (age >= 18) {
console.log("You are eligible to vote.");
}

? if else Statement

? View Code Example 
// Login status check
let isLoggedIn = false;
if (isLoggedIn) {
console.log("Welcome back!");
} else {
console.log("Please log in.");
}

? else if Statement

? View Code Example 
// Grade calculation
let score = 65;
if (score >= 90) {
console.log("Grade: A");
} else if (score >= 80) {
console.log("Grade: B");
} else if (score >= 70) {
console.log("Grade: C");
} else {
console.log("Grade: F");
}

? switch Statement

? View Code Example 
// Day name finder
let day = 3;
let dayName = "";
switch (day) {
case 1:
dayName = "Monday";
break;
case 2:
dayName = "Tuesday";
break;
case 3:
dayName = "Wednesday";
break;
case 4:
dayName = "Thursday";
break;
case 5:
dayName = "Friday";
break;
default:
dayName = "Weekend";
}
console.log(dayName);

? switch Calculator Example

? View Code Example 
// Simple calculator
let a = 8, b = 2, operator = "/";
switch (operator) {
case "+":
console.log("Result:", a + b);
break;
case "-":
console.log("Result:", a - b);
break;
case "*":
console.log("Result:", a * b);
break;
case "/":
console.log("Result:", a / b);
break;
default:
console.log("Invalid operator");
}

? When to Use What

  • if – single checks
  • if else – two outcomes
  • else if – multi-level logic
  • switch – exact matches

? Live Output / Explanation

? Output Summary

  • If: prints eligibility message
  • If else: prints login prompt
  • Else if: prints grade F
  • Switch: prints Wednesday
  • Calculator: prints Result: 4

? Interactive Example

Uses an if else condition

? Result

Enter age and click button

? Tips & Best Practices

  • Keep conditions simple
  • Use else if for ranges
  • Always include break in switch
  • Use switch for fixed values

? Try It Yourself

  • Check if a number is positive, negative, or zero
  • Determine traffic light action (red, yellow, green)
  • Calculate shipping cost based on region
  • Validate password strength (weak, medium, strong)
  • Compare two numbers and return the larger one