Switch Statement in JavaScript

Basic Syntax of a Switch Statement

switch (expression) {
    case value1:
        // code block to execute
        break;
    case value2:
        // code block to execute
        break;
    default:
        // code block to execute if no cases match
}

In this syntax, the expression is evaluated once, and its value is compared with each case. If there is a match, the corresponding code block is executed.

Example of a Switch Statement

const day = 3;
let dayName;

switch (day) {
    case 1:
        dayName = "Monday";
        break;
    case 2:
        dayName = "Tuesday";
        break;
    case 3:
        dayName = "Wednesday";
        break;
    default:
        dayName = "Invalid day";
}

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

In this example, the variable day is matched against several cases, and the corresponding day name is assigned to dayName.

Omitting Break Statements

If you omit the break statement, the code will continue executing into the next case, which can be useful in certain situations:

const score = 85;
let grade;

switch (true) {
    case score >= 90:
        grade = "A";
        break;
    case score >= 80:
        grade = "B";
    case score >= 70:
        grade = "C";
        break;
    default:
        grade = "F";
}

console.log(grade); // Output: B

In this example, since there is no break after case 80, both cases for 'B' and 'C' are executed if the score is 80 or higher.

Default Case

The default case is executed if none of the specified cases match the expression:

const fruit = "banana";

switch (fruit) {
    case "apple":
        console.log("Apple pie!");
        break;
    case "banana":
        console.log("Banana smoothie!");
        break;
    default:
        console.log("Fruit not found.");
}

If the fruit variable matches "banana", the output will be "Banana smoothie!"

Conclusion

The switch statement is a useful alternative to multiple if statements, making code cleaner and easier to read when dealing with multiple conditions. However, it's important to remember to include break statements to avoid unintentional fall-through behavior.