防止在基本银行应用程序上重置总数

Question

我正在为初级 JS 课程开发一个基本的银行应用程序。

预期：

• 用户单击调用银行应用程序功能的按钮，使用 switch 语句选择提款、存款、检查余额或退出
• 选择提现或存款后，系统会提示他们添加金额
• 在控制台登录出入金金额和新余额
• 随后的每次按钮点击和提款/存款都应跟踪余额

实际：

• 由于 switch 语句，小计正在重置，我不知道如何在不删除中断的情况下保持运行总计。

有没有办法调整此代码以保持运行平衡？

function bankingApp() {
  let currentBalance = 0;
  let userPrompt = prompt(
    "bank menu: w = withdrawal | d = deposit | b = balance |  q = quit"
  );

  switch (userPrompt) {
    case "w":
      function withdrawFunds() {
        let withdrawAmount = parseFloat(prompt("Withdraw amount: "));
        currentBalance = currentBalance - withdrawAmount;
        console.log(
          "Withdraw: " + withdrawAmount + "New balance: " + currentBalance
        );
      }
      withdrawFunds();
      break;

    case "d":
      function depositFunds() {
        let depositAmount = parseFloat(prompt("Deposit amount:"));
        console.log(
          "Deposit: " + depositAmount + "New balance: " + currentBalance
        );
      }
      depositFunds();
      break;

    case "b":
      function checkBalance() {
        let balance = currentBalance;
        console.log(balance);
      }
      checkBalance();
      break;

    case "q":
      function quitProgram() {
        let quit = "Quit the program.";
        console.log(quit);
      }
      quitProgram();
      break;

    default:
      console.log("That menu is not available.");
  }
}

Answer 1

您在事件发生时调用您的函数（按钮单击）。现在，您的函数中的第一条语句将余额设置为 0。没有任何东西可以跟踪它。

只需将语句移出，变量就会持续存在。

let currentBalance = 0;

function bankingApp() {

  let userPrompt = prompt(
    "bank menu: w = withdrawal | d = deposit | b = balance |  q = quit"
  );

  switch (userPrompt) {
    case "w":
      function withdrawFunds() {
        let withdrawAmount = parseFloat(prompt("Withdraw amount: "));
        currentBalance = currentBalance - withdrawAmount;
        console.log(
          "Withdraw: " + withdrawAmount + "New balance: " + currentBalance
        );
      }
      withdrawFunds();
      break;

    case "d":
      function depositFunds() {
        let depositAmount = parseFloat(prompt("Deposit amount:"));
        console.log(
          "Deposit: " + depositAmount + "New balance: " + currentBalance
        );
      }
      depositFunds();
      break;

    case "b":
      function checkBalance() {
        let balance = currentBalance;
        console.log(balance);
      }
      checkBalance();
      break;

    case "q":
      function quitProgram() {
        let quit = "Quit the program.";
        console.log(quit);
      }
      quitProgram();
      break;

    default:
      console.log("That menu is not available.");
  }
}