In JavaScript, a switch statement is a control flow statement that allows you to execute different code blocks based on the value of an expression.  A switch statement tests the value of an expression against multiple cases. It is an alternative to using multiple if-else statements.

switch (expression) {
  case value1:
    // Code to be executed if expression matches value1
    break;
  case value2:
    // Code to be executed if expression matches value2
    break;
  case value3:
    // Code to be executed if expression matches value3
    break;
  default:
    // Code to be executed if expression doesn't match any of the cases
    break;
}

In this example, the variable grade represents the grade of a student. The switch statement checks the value of grade and assigns a corresponding message to the message variable.

If grade is set to "B", the output will be "Good job!".

 

    let grade = "B";
    let message;

    switch (grade) {
    case "A":
        message = "Excellent job!";
        break;
    case "B":
        message = "Good job!";
        break;
    case "C":
        message = "Fair job!";
        break;
    case "D":
        message = "Needs improvement.";
        break;
    case "F":
        message = "Failed.";
        break;
    default:
        message = "Invalid grade.";
    }

    console.log(message);

 Switch statement with dynamic user input

 var fruit = prompt("Enter a fruit:");

 switch (fruit.toLowerCase()) {
    case "apple":
        console.log("The fruit is an apple");
        break;
    case "banana":
        console.log("The fruit is a banana");
        break;
    case "orange":
        console.log("The fruit is an orange");
        break;
    default:
        console.log("Unknown fruit");
        break;
    }

Switch statement with a dynamic expression

   
 function getVehicleType(vehicle) {
        switch (true) {
        case vehicle instanceof Car:
            return "Car";
        case vehicle instanceof Motorcycle:
            return "Motorcycle";
        case vehicle instanceof Bicycle:
            return "Bicycle";
        default:
            return "Unknown";
        }
    }
    
    function Car() {}
    function Motorcycle() {}
    function Bicycle() {}
    
    var vehicle1 = new Car();
    var vehicle2 = new Motorcycle();
    var vehicle3 = new Bicycle();
    
    console.log(getVehicleType(vehicle1)); // Output: Car
    console.log(getVehicleType(vehicle2)); // Output: Motorcycle
    console.log(getVehicleType(vehicle3)); // Output: Bicycle
    console.log(getVehicleType("boat"));    // Output: Unknown