Código da Resolução do Exercício

index.html

<html>
<head>
    <meta />
    <meta name="viewport" />
    <meta />
    <title>Exercício 09</title>
</head>
<body>
    Exercitando Funções
</body>
</html>

index.js

let spaceshipName = prompt("Digite o nome da nave")
let spaceshipVelocity = 0
let chosenOption
function showMenu() {
    let option
    while(option != "1" && option != "2" && option != "3" && option != "4") {
        option = prompt("O que deseja fazer?\\n" +
                        "1- Acelerar a nave em 5km/s\\n" +
                        "2- Desacelerar a nave em 5km/s\\n" +
                        "3- Imprimir dados de bordo\\n" +
                        "4- Sair de programa")
    }
    return option
}
function speedUp(velocity) {
    let newVelocity = velocity + 5
    return newVelocity
}
function slowDown(velocity) {
    let newVelocity = velocity - 5
    if(newVelocity < 0) {
        newVelocity = 0
    }
    return newVelocity
}
function printSpaceshipBoardData(name, velocity) {
    alert("Espaçonave: " + name + "\\nVelocidade: " + velocity + "km/s")
}
do {
    chosenOption = showMenu()
    switch(chosenOption) {
        case "1":
            spaceshipVelocity = speedUp(spaceshipVelocity)
            break
        case "2":
            spaceshipVelocity = slowDown(spaceshipVelocity)
            break
        case "3":
            printSpaceshipBoardData(spaceshipName, spaceshipVelocity)
            break
        default:
            alert("Encerrando programa de bordo")
    }
} while(chosenOption != "4")