# 10. switch Statement

In JavaScript, the `switch` statement is used for making decisions based on the value of an expression. It provides a way to compare a single value against multiple possible case values and execute code blocks based on which case value matches the value of the expression. Here's the basic syntax of the `switch` statement:

```javascript
switch (expression) {
    case value1:
        // Code to execute if expression matches value1
        break;
    case value2:
        // Code to execute if expression matches value2
        break;
    // Additional cases can be added as needed.
    default:
        // Code to execute if none of the cases match the expression
}
```

Here's a breakdown of how it works:

1. The `switch` keyword is followed by an expression enclosed in parentheses. This expression is the value that you want to compare against the different case values.

2. Inside the `switch` block, you define one or more `case` blocks. Each `case` block specifies a value that you want to compare with the expression. If the expression matches a `case` value, the code inside that `case` block will be executed.

3. After each `case` block, you typically include a `break` statement. This `break` statement is used to exit the `switch` statement after executing the code in the matching `case`. Without a `break` statement, the `switch` statement would continue to execute the code in subsequent `case` blocks.

4. You can also include a `default` block at the end of the `switch` statement. The `default` block is executed if none of the `case` values match the expression.

Here's an example:

```javascript
let day = "Monday";

switch (day) {
    case "Monday":
        console.log("It's the start of the workweek.");
        break;
    case "Friday":
        console.log("It's almost the weekend.");
        break;
    default:
        console.log("It's a regular day.");
}
```

In this example, the `switch` statement compares the value of the `day` variable against different cases and prints a message based on the value of `day`. Since `day` is "Monday" in this case, it will print "It's the start of the workweek."

The `switch` statement is useful when you have multiple conditions to check against a single expression, and it can provide a cleaner and more efficient way to handle these situations compared to using a series of `if/else if` statements.

## Example
```js
const number = parseInt(prompt('Enter a number between 1 to 7: '));

switch (number) {
    case 1:
        console.log("Sunday");
        break;
    case 2:
        console.log("Monday");
        break;
    case 3:
        console.log("Tuesday");
        break;
    case 4:
        console.log("Wednesday");
        break;
    case 5:
        console.log("Thursday");
        break;
    case 6:
        console.log("Friday");
        break;
    case 7:
        console.log("Saturday");
        break;
    default:
        console.log("Invalid Number");
}
```
**Output**
```
Enter a number between 1 to 7: 4
Wednesday
```
***
## Omitting break
```js
const number = parseInt(prompt('Enter a number between 1 to 7: '));

switch (number) {
    case 1:
        console.log("Sunday");
    case 2:
        console.log("Monday");
    case 3:
        console.log("Tuesday");
    case 4:
        console.log("Wednesday");
    case 5:
        console.log("Thursday");
    case 6:
        console.log("Friday");
    case 7:
        console.log("Saturday");
    default:
        console.log("Invalid Number");
}
```
**Output**
```
Wednesday
Thursday
Friday
Saturday
Invalid Number
```
***
## JavaScript switch With Multiple Case
```js
const day = prompt('Enter the day: ');

switch (day) {
    case 'Monday':
    case 'Tuesday':
    case 'Wednesday':
    case 'Thursday':;
    case 'Friday':
        console.log("Weekday");
        break;
    case 'Saturday':
    case 'Sunday':
        console.log("Weekend");
        break;
    default:
        console.log("Invalid Day");
}
```
**Output**
```
Weekday
```
## Simple Calculator
```js
// take the operator input
const operator = prompt('Enter operator ( either +, -, * or / ): ');

// take the operand input
const number1 = parseFloat(prompt('Enter first number: '));
const number2 = parseFloat(prompt('Enter second number: '));

let result;
switch(operator) {
    case '+':
        result = number1 + number2;
        break;
    case '-':
        result = number1 - number2;
        break;
    case '*':
        result = number1 * number2;
        break;
    case '/':
        result = number1 / number2;
        break;

    default:
        console.log('Invalid operator');
        break;
}
console.log(`${number1} ${operator} ${number2} = ${result}`);
```
**Output**
```
Enter operator: *
Enter first number: 5
Enter second number: 8.8
5 * 8.8 = 44
```
***
## Assignment and Task
**Can you use switch statements to create a program that takes the number input from the user from 1 to 12. And, print the corresponding month based on the input value.**
### Solution:
```js
const number = parseInt(prompt('Enter a number from 1 to 12: '));

let result;
switch(number) {
    case 1:
        result = "January";
        break;
    case 2:
        result = "Febraury";
        break;
    case 3:
        result = "March";
        break;
    case 4:
        result = "April";
        break;
    case 5:
        result = "May";
        break;
    case 6:
        result = "June";
        break;
    case 7:
        result = "July";
        break;
    case 8:
        result = "August";
        break;
    case 9:
        result = "September";
        break;
    case 10:
        result = "October";
        break;
    case 11:
        result = "November";
        break;
    case 12:
        result = "December";
        break;
    default:
        console.log('Invalid number');
        break;
}
console.log(result);
```
**Output**
```
Enter a number from 1 to 12: 3
March
```
***
## p4n Quiz 
**Q. Which of the cases is executed in the following code?**
```js
let value = 4;

switch(value) {
  case 1:
  case 2:
  default:
}
```
1. case 1
2. case 2
3. case 4
4. default

Answer: 4