A switch statement is a control flow statement used in programming that allows a value to be tested against a list of cases. It is similar to an if-else statement but is more concise and can be easier to read for certain scenarios.
The switch statement takes an expression as an input, which is evaluated against multiple cases. Each case consists of a specific value or a range of values to compare the expression against. If the expression matches a case, the statements associated with that case are executed. If there is no match, a default case is executed (if provided).
We need break statements in switch statements to ensure that only the code corresponding to the matching case statement is executed and the execution of the switch statement is terminated. Without a break statement, execution will "fall through" to the next case statement and possibly execute that code as well. This can lead to unexpected behavior and bugs in the program.
<!DOCTYPE html>
<html>
<head>
<!-- <script src="main.js"></script> -->
</head>
<body>
<script>
var option = "a";
switch(option) {
case "a":
document.write("User needs A");
break;
case "b":
document.write("User needs B");
break;
case "c":
document.write("User needs C");
break;
default:
alert("I am from default");
}
</script>
</body>
</html>
This is code that uses a switch statement to check the value of the variable option. The switch statement tests the value of the expression (option) against multiple cases.
In this example, the value of option is "a". The switch statement checks the value of option against three cases: "a", "b", and "c". Since option matches the first case, "a", the code inside that case is executed. In this case, it writes the message "User needs A" to the document using document.write().
After the case is executed, the break statement terminates the switch statement, preventing execution of the other cases. If none of the cases match, the default case is executed. In this example, it displays an alert message "I am from default".
Switch statements are useful in situations where you need to evaluate a variable or an expression against a series of possible values and take different actions based on the value. They can help simplify code and improve performance compared to using multiple if-else statements.
For example, switch statements are commonly used in menu systems, where different options may trigger different actions based on the user's selection. They are also used in data processing and analysis, where different types of data may require different processing logic.
The default keyword is used to define the default case that will be executed if none of the cases match the input value. It is similar to the else clause in an if-else statement.
If none of the cases match the input value, the code in the default block will be executed. The default case is optional, and it is not necessary to include it in a switch statement. However, it is considered good practice to include a default case to handle unexpected input values.
