Explain Javascript Switch Statement

The switch statement in JavaScript is used to execute one block of code among many options. It is an alternative to using multiple if...else if statements, making the code more readable and easier to manage when dealing with multiple possible values for a single variable.

Here's the basic syntax of a switch statement:

switch (expression) {
  case value1:
    // Code to be executed if expression === value1
    break;
  case value2:
    // Code to be executed if expression === value2
    break;
  // You can have as many cases as needed
  default:
    // Code to be executed if expression doesn't match any case
}

Example 1: Basic Switch Statement

Let's use a switch statement to display the name of the day based on a number (0 for Sunday, 1 for Monday, etc.).

let day = 3;
let dayName;

switch (day) {
  case 0:
    dayName = "Sunday";
    break;
  case 1:
    dayName = "Monday";
    break;
  case 2:
    dayName = "Tuesday";
    break;
  case 3:
    dayName = "Wednesday";
    break;
  case 4:
    dayName = "Thursday";
    break;
  case 5:
    dayName = "Friday";
    break;
  case 6:
    dayName = "Saturday";
    break;
  default:
    dayName = "Invalid day";
}

console.log(dayName); // Output: Wednesday

Example 2: Using Default Case

If the value of the expression doesn't match any of the specified cases, the code inside the default case will be executed.

let fruit = "Mango";
let color;

switch (fruit) {
  case "Banana":
    color = "Yellow";
    break;
  case "Apple":
    color = "Red";
    break;
  case "Grapes":
    color = "Purple";
    break;
  default:
    color = "Unknown";
}

console.log(color); // Output: Unknown

Example 3: Grouping Cases

You can group cases to execute the same code for multiple values.

let animal = "Dog";
let sound;

switch (animal) {
  case "Cow":
  case "Goat":
  case "Sheep":
    sound = "Baa";
    break;
  case "Dog":
  case "Cat":
    sound = "Woof or Meow";
    break;
  default:
    sound = "Unknown sound";
}

console.log(sound); // Output: Woof or Meow

Example 4: Fall-Through

If you omit the break statement, the code will continue to execute the following cases until a break is encountered. This is known as "fall-through."

let grade = 'B';
let message;

switch (grade) {
  case 'A':
    message = "Excellent";
    break;
  case 'B':
  case 'C':
    message = "Well done";
    break;
  case 'D':
    message = "You passed";
    break;
  case 'F':
    message = "Better try again";
    break;
  default:
    message = "Unknown grade";
}

console.log(message); // Output: Well done

In this example, both 'B' and 'C' will result in the message "Well done" because the case 'C': does not have a break and thus "falls through" to the case 'B': block.

Using the switch statement can make your code cleaner and easier to understand when dealing with multiple possible values for a single variable.