Chapter 4 · Lesson 1

Conditional Statements

Conditional statements let your code make decisions based on conditions.

if Statement: Executes a block of code if the condition is true.

if...else Statement: Executes one block if true, another if false.

if...else if...else: Chain multiple conditions together.

Ternary Operator: Shorthand for simple if/else: condition ? trueValue : falseValue

switch Statement: Compare a value against multiple cases. Good for multiple specific values.

Best Practices:

Keep conditions simple and readable
Use early returns to reduce nesting
Consider switch for 3+ conditions on the same value
Use the ternary operator only for simple expressions

Code Examples

If/Else Statementsjavascript

// Simple if
let age = 20;

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

// if...else
let temperature = 15;

if (temperature > 25) {
  console.log("It's hot!");
} else {
  console.log("It's not hot");
}

// if...else if...else
let score = 85;

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");
}

// Ternary operator
let status = age >= 18 ? "adult" : "minor";
console.log("Status:", status);

// Nested ternary (use sparingly!)
let category = age < 13 ? "child" : age < 20 ? "teen" : "adult";
console.log("Category:", category);

The ternary operator is great for simple conditions, but use if/else for complex logic to maintain readability.

Switch Statementjavascript

let day = "Monday";

switch (day) {
  case "Monday":
    console.log("Start of the work week");
    break;
  case "Tuesday":
  case "Wednesday":
  case "Thursday":
    console.log("Midweek");
    break;
  case "Friday":
    console.log("TGIF!");
    break;
  case "Saturday":
  case "Sunday":
    console.log("Weekend!");
    break;
  default:
    console.log("Invalid day");
}

// Switch with expressions (less common but useful)
let grade = "B";
let message;

switch (true) {
  case grade === "A":
    message = "Excellent!";
    break;
  case grade === "B" || grade === "C":
    message = "Good job!";
    break;
  default:
    message = "Keep trying!";
}

console.log(message);

Don't forget the break statement! Without it, execution 'falls through' to the next case.

Quick Quiz

1. What happens if you forget 'break' in a switch statement?

2. What is the ternary operator syntax?

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