JavaScript

The if, else, and else if statements are used to perform conditional logic in JavaScript. They allow your code to make decisions based on different conditions.

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✅ Basic if Statement

The if statement runs a block of code only if a specified condition is true.

if (condition) {
  // Code to run if condition is true
}

Example:

let age = 20;

if (age >= 18) {
  console.log("You are an adult.");
}

Output:

You are an adult.

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🔁 if...else Statement

Use else to run a block of code if the condition is false.

if (condition) {
  // Run this if true
} else {
  // Run this if false
}

Example:

let isLoggedIn = false;

if (isLoggedIn) {
  console.log("Welcome back!");
} else {
  console.log("Please log in.");
}

Output:

Please log in.

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🔄 if...else if...else Statement

When you need to check multiple conditions, use else if.

if (condition1) {
  // Run if condition1 is true
} else if (condition2) {
  // Run if condition2 is true
} else {
  // Run if none are true
}

Example:

let score = 75;

if (score >= 90) {
  console.log("Grade: A");
} else if (score >= 70) {
  console.log("Grade: B");
} else {
  console.log("Grade: C or below");
}

Output:

Grade: B

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🧪 Nested if Statements

You can place if statements inside other if blocks.

let user = "admin";
let loggedIn = true;

if (loggedIn) {
  if (user === "admin") {
    console.log("Welcome, Admin!");
  }
}

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🔐 Practical Example: Login Check

let username = "john";
let password = "12345";

if (username === "john" && password === "12345") {
  console.log("Login successful!");
} else {
  console.log("Invalid credentials.");
}

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📌 Summary

• Use if to run code when a condition is true.
• Use else to handle the false case.
• Use else if to test multiple conditions.
• You can nest if statements for more complex logic.

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