如何在 switch 语句中显示用户输入？

Question

我目前正忙于用户列表挑战，这就是挑战：

-向数据库添加 3 个新用户（通过用户输入获取，而不是硬编码） - 通过索引从数据库中删除用户。（用户输入，无硬编码） -concatenate/merge 将数据库中的所有用户名合并为一个字符串并在-the DOM 中适当显示 - 按字母顺序对数据库中的用户名进行排序并将其注销到控制台

这是我的代码：

let userlist = ["Steven", "Michael","Sarah","Lisa","Tamryn", "Wayne","Kirsten", "Peter", "Gwen", "Tamzin"];
console.log(userlist);

let menu = (prompt("=====Menu=====\n 1.Add three users\n 2.Remove User\n 3.Display All users\n 4.Sort users\n")-1);

switch(userlist)
{

    case 0: 
    let newUsers = prompt("Add three user");
    userlist.push(newUsers);

    break;
    case 1:
    let removeUser = prompt("Remove a User");
    newUsers = userlist.indexOf(removeUser);
    let removedUser = userlist.splice(newUsers,1);

    console.log(indexRemoved + " " + removedUser); 
    alert(`${removedUser} has been removed from the database`);
    break;
    case 2:
    let display =  prompt("Display a User");

    break;
    case 3:
    let sort = prompt("Sort users")
    break;
    default:
        alert("Please select 1 - 4 to choose any of the options displayed.");
        break;
}

我不确定如何实现后两种情况

Answer 1

我已经更正了您程序中的一些错误，但您编写的某些功能中仍有一些错误需要更正。这只是为了为您的应用程序提供一个工作框架。

主要变化：

您需要将输入解析为 number 否则您的开关将无法正常工作
您需要打开 menu 而不是 userlist 的解析值，因为 userlist 是一个数组，您正试图将其与 number 进行比较你的switch声明
我在您的应用程序中添加了一个无限循环，这意味着用户总是会在某些选项被 select 编辑后返回到菜单，并且可以 select 他/她的下一件事想做。为了能够退出这个循环，我添加了一个 Exit 选项来结束应用程序。

您现在可以运行申请。添加用户以及显示用户应该可以工作。

let userlist = [
  "Steven",
  "Michael",
  "Sarah",
  "Lisa",
  "Tamryn",
  "Wayne",
  "Kirsten",
  "Peter",
  "Gwen",
  "Tamzin",
];
console.log(userlist);

// make program run indefinitely (until tab/ browser is closed or Exit option is selected)
let exit = false;
while (true) {
  let menu = prompt(
    "=====Menu=====\n 1. Add an user\n 2. Remove user\n 3. Display all users\n 4. Sort users\n 5. Exit\n"
  )
  // Parse result as Integer
  // you did it with -1, but it would be more natural to just parse the number as displayed on the screen and adjust the values in the switch accordingly
  menu = Number.parseInt(menu) - 1;
  if(isNaN(menu)){
      // something else than a number was entered
      alert("You must enter a number!")
      // move on to next iteration => means here: display menu again.
      continue;
  }

  // now use menu to determine which option was choosen
  switch (menu) {
    case 0:
      // added an instruction so a user knows what to do
      let newUsers = prompt("Add a user: \nPlease provide a username");
      userlist.push(newUsers);
      break;
    case 1:
      // added an instruction so a user knows what to do
      let removeUser = prompt(
        "==Remove a User==\nPlease provide the hame of the user you want to delete"
      );
      newUsers = userlist.indexOf(removeUser);
      let removedUser = userlist.splice(newUsers, 1);

      console.log(indexRemoved + " " + removedUser);
      alert(`${removedUser} has been removed from the database`);
      break;
    case 2:
      alert(`Display all users:\n ${userlist}`);
      break;
    case 3:
      let sort = prompt("Sort users");
      // todo
      break;
    case 4:
        exit = true;
        break;
    default:
      alert("Please select 1 - 4 to choose any of the options displayed.");
      break;
  }
  // if user wants to exit the program break the infinite loop
  if(exit){
      exit = false;
      break;
  }
}

Answer 2

您的结果存储在 menu 变量中，因此您的开关应该比较此变量，而不是 userlist。

您只需按原样进行切换 =>

switch(menu)

如何在 switch 语句中显示用户输入？

how to display user input in a switch statement?

javascript

switch-statement