Understanding the Default Case of Switch Statements

The default case in a switch statement is executed when all the other cases evaluate to false.

In programming, switch statements are used for decision making. They check a variable or an expression against various values (cases) defined in the switch block, and the code associated with the matching case is executed. If none of the cases match, then the code under the default case is executed.

Let's take a look at this with an example.

let dayNumber = 7;

switch (dayNumber) {
    case 0:
        console.log("Sunday");
        break;
    case 1:
        console.log("Monday");
        break;
    case 2:
        console.log("Tuesday");
        break;
    // ...
    default:
        console.log("Invalid day");
        break;
}

In this scenario, we're checking the variable dayNumber against different days of the week. The dayNumber provided in our example is 7, which doesn't match any of the cases within our switch statement. Because no match is found, the default case console.log("Invalid day"); is executed.

It's important to include a default case in your switch statement as a best practice. It accounts for unexpected values and helps maintain the robustness of your code. It's also a strategic way of handling errors or unanticipated inputs, without letting the program fail.

Remember, it doesn't matter where in the switch statement the default case is placed, as it will always execute if no other cases match, regardless of its position. However, it is conventional to place the default case at the end of the switch block for the sake of clarity and readability.