JavaScript

The switch statement is used to perform different actions based on different conditions. It’s a cleaner way to write multiple if...else if statements when checking the same variable or expression.

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✅ Syntax

switch (expression) {
  case value1:
    // Code to run if expression === value1
    break;
  case value2:
    // Code to run if expression === value2
    break;
  ...
  default:
    // Code to run if no case matches
}

• break stops the execution after a case is matched.
• default is optional and runs when no case matches.

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🔍 Example:

let day = "Tuesday";

switch (day) {
  case "Monday":
    console.log("Start of the week.");
    break;
  case "Tuesday":
    console.log("It's Tuesday!");
    break;
  case "Wednesday":
    console.log("Halfway there.");
    break;
  default:
    console.log("Another day.");
}

Output:

It's Tuesday!

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⚠️ Why use break?

If you don’t use break, JavaScript will continue to run the next cases, even if a match is found.

let fruit = "apple";

switch (fruit) {
  case "apple":
    console.log("Apples are red.");
  case "banana":
    console.log("Bananas are yellow.");
  default:
    console.log("Fruit not found.");
}

Output:

Apples are red.
Bananas are yellow.
Fruit not found.

✅ To fix it, add break after each case.

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🔁 Using default

The default case is like the else block. It runs when none of the other cases match.

let color = "blue";

switch (color) {
  case "red":
    console.log("Stop!");
    break;
  case "green":
    console.log("Go!");
    break;
  default:
    console.log("Unknown color.");
}

Output:

Unknown color.

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🔢 Example with Numbers

let grade = 90;

switch (true) {
  case (grade >= 90):
    console.log("Grade A");
    break;
  case (grade >= 80):
    console.log("Grade B");
    break;
  default:
    console.log("Keep trying!");
}

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📌 Summary

• switch is used when checking a single expression against multiple values.
• Each case must end with a break (to avoid fall-through).
• Use default for unmatched conditions.

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