Switch Statement

Think about calling a customer care number:

"Press 1 for balance enquiry. Press 2 for recharge. Press 3 to talk to an agent."

Based on the one number you press, the system takes you to the right option.

In the last lesson, we learned if...else if...else. We could write this menu with it:

It works, but we keep repeating choice === ... again and again. When one value is compared with many fixed options, JavaScript gives us a cleaner tool: the switch statement.

What Is a Switch Statement?

A switch statement checks one value against many possible matches (called cases), and runs the code of the case that matches.

Syntax

switch (expression) {
  case value1:
    // runs if expression === value1
    break;

  case value2:
    // runs if expression === value2
    break;

  default:
    // runs if nothing matches
}

The parts:

A Simple Example

Let us rewrite the customer care menu using switch:

Output:

Recharge

How it works, step by step:

1. JavaScript takes the value of choice, which is 2.
2. It checks case 1. No match, so it moves on.
3. It checks case 2. It matches! ✅ It runs console.log("Recharge").
4. It sees break and exits the switch.

Another Example: Day of the Week

Why Is break So Important?

break tells JavaScript: "Work is done, exit the switch now."

If you forget break, JavaScript does not stop. It keeps running all the cases below it, even if they don't match! This is called fall-through.

❌ Without break:

😮 It matched "yellow", but it also ran "green" and default!

Think of it like falling down a staircase. Once you slip at one step, you keep rolling down until something stops you. break is that railing.

✅ With break:

Rule: Always add break at the end of every case, unless you want fall-through on purpose.

Using Fall-Through on Purpose: Grouping Cases

Sometimes many values should give the same result. You can stack cases together without break between them.

Example: weekday or weekend

Example: seasons in India

This is much shorter than writing month === "June" || month === "July" || ... in an if statement.

The default Case

default runs when no case matches. It works just like the final else.

Key points:

• default is optional, but it is good practice to always include it.
• It is usually written at the end, so it doesn't need a break.
• If you write default in the middle, add a break after it to avoid fall-through.

Switch Uses Strict Comparison (===)

switch compares values using ===, so both the value and the type must match.

"1" (string) is not equal to 1 (number) with ===.

Fix: Convert the value first, using what you learned in Type Casting:

switch (Number(input)) {
  case 1:
    console.log("You pressed one");   // ✅ now it matches
    break;
}

Checking Ranges with switch (true)

A normal switch checks exact values, not ranges like marks >= 90. But there is a trick: use switch (true), and write a condition in each case.

JavaScript finds the first case that is true.

Note: This works, but for ranges, if...else if is usually easier to read. Use switch mainly for exact values.

Declaring Variables Inside Cases

All cases share the same block { }. So declaring the same variable name in two cases gives an error:

switch (choice) {
  case 1:
    let message = "One";     // ❌
    break;
  case 2:
    let message = "Two";     // ❌ SyntaxError: already declared
    break;
}

Fix: Wrap each case in its own curly braces:

switch (choice) {
  case 1: {
    let message = "One";   ✅
    console.log(message);
    break;
  }
  case 2: {
    let message = "Two";   ✅
    console.log(message);
    break;
  }
}

Switch vs If-Else: When to Use Which?

Simple way to remember:

• Menu-style choices (1, 2, 3 or "red", "green") → switch
• Questions with conditions (is it greater than? is it between?) → if...else

Common Mistakes to Avoid

Key Takeaways

• A switch statement compares one value with many cases and runs the one that matches.
• Always use break to exit after a match, otherwise the code falls through to the next cases.
• Group cases together when many values should give the same result.
• switch uses strict comparison (===), so the value and the type must both match.
• Use switch for fixed, menu-style choices, and if...else for ranges and complex conditions.