Lesson 2: if, else if, and else Statements

Learning Objectives

By the end of this lesson, learners will:

• Understand how to make decisions in JavaScript using if, else if, and else
• Learn the correct syntax for conditional statements
• Create programs that react to different conditions
• Understand the importance of using comparison operators inside conditions
• Apply logic to real-world decision-making examples

Why Use if Statements?

Sometimes, you only want to run a piece of code if a certain condition is true.

For example:

• Show a special message if a user is logged in
• Charge extra if shipping is international
• Display “Good morning” if it’s before noon

This is where the if, else if, and else statements come into play.

1. Basic if Statement

Syntax:

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

Example:

let age = 18;

if (age >= 18) {
  console.log("You can vote!");
}

In this example:

• age >= 18 is the condition
• "You can vote!" is only printed if the condition is true

2. else Statement

The else block runs if the condition is false.

Syntax:

if (condition) {
  // run if true
} else {
  // run if false
}

Example:

let isRaining = false;

if (isRaining) {
  console.log("Take an umbrella.");
} else {
  console.log("Enjoy the sunshine!");
}

🧠 Only one of the blocks will run, never both.

3. else if Statement

Use else if to check multiple conditions, one after the other.

Syntax:

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

Example:

let score = 72;

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");
}

🧠 JavaScript checks each condition in order, top to bottom, and runs the first one that is true.

Important Syntax Rules

• Use parentheses () for the condition
• Use curly braces {} to define the code block
• You can nest if statements, but keep it readable

Real-Life Example

Clothing Suggestion App:

let temperature = 15;

if (temperature > 25) {
  console.log("Wear a t-shirt.");
} else if (temperature > 15) {
  console.log("Wear a light jacket.");
} else {
  console.log("Wear a coat.");
}

This shows how JavaScript can adapt based on real-world data.

Practice Activity

Try this in your browser console:

let time = 20;

if (time < 12) {
  console.log("Good morning");
} else if (time < 18) {
  console.log("Good afternoon");
} else {
  console.log("Good evening");
}

🧠 Output: "Good evening"

Logical Operators in Conditions

You can combine multiple conditions using:

Key Takeaways

• if checks a condition — code runs only if it’s true
• else handles the opposite — runs when the if condition is false
• else if allows for multiple possible outcomes
• Use logical operators for more complex decisions