Javascript：循环结束后的警报消息答案

【问题标题】：Javascript: Alert message after loop endsJavascript：循环结束后的警报消息
【发布时间】：2019-04-28 15:56:13
【问题描述】：

这是一个简单的学校登录练习。它旨在让您尝试登录 3 次。我想在循环停止后（使用了 3 次尝试），提醒用户他没有剩余尝试，他的帐户将被阻止。

类似：

alert("You don't have any attempts left. Your account is now blocked);

这是我制作的循环：

var tries;

for (tries = 2; tries !== -1; tries--) {
    let User = prompt("Enter your username:");
    let Pass = prompt("Enter your password:");
        if (User === "hello" && Pass === "world") {
            alert("Welcome.");
            break;
        } else {
            alert("Incorrect username and/or password. You have " + tries + " attempt(s) left.");
        }
}

提前致谢。

【问题讨论】：

这段代码会发生什么？它永远循环？您必须让我们知道问题出在哪里，您尝试了什么以及问题出在哪里。提示：!== 与 != 不同。见stackoverflow.com/questions/1946063/in-javascript-is-same-as

标签： javascript for-loop

【解决方案1】：

你离得很近。我想这就是你想要的。

var tries;

for (tries = 2; tries >= 0; tries--) {
    let User = prompt("Enter your username:");
    let Pass = prompt("Enter your password:");
        if (User === "hello" && Pass === "world") {
            alert("Welcome.");
            break;
        } else if (tries == 0) {
            alert("You don't have any attempts left. Your account is now blocked");
        }  else {
            alert("Incorrect username and/or password. You have " + tries + " attempt(s) left.");
        }
}

【讨论】：

谢谢！这正是我所需要的。

【解决方案2】：

您可以递归地实现这一点。每次输入错误的用户名或密码时，只需减少尝试次数即可。

var TRIES = 3;

function ask() {
  let User = prompt("Enter your username:");
  let Pass = prompt("Enter your password:");

  if (User === "hello" && Pass === "world") {
    return alert("Welcome.");
  }

  if (TRIES > 0) {
    alert("Incorrect username and/or password. You have " + TRIES + " attempt(s) left.");
    TRIES -= 1;
    ask()
  } else {
    alert("You don't have any attempts left. Your account is now blocked");
  }
}

ask()

【讨论】：

【解决方案3】：

var tries;

for (tries = 0; tries < 3; tries++) {
    let User = prompt("Enter your username:");
    let Pass = prompt("Enter your password:");
        if (User === "hello" && Pass === "world") {
            alert("Welcome.");
            break;
        } else {
            alert("Incorrect username and/or password. You have " + tries + " attempt(s) left.");
        }
        if(tries == 2)
        {
            alert("You don't have any attempts left. Your account is now blocked);
        }
}

【讨论】：

【解决方案4】：

也许您可以通过以下方式实现：

for (var attemptsRemaining = 3; attemptsRemaining > 0; attemptsRemaining--) {
  
    let User = prompt("Enter your username:");
    let Pass = prompt("Enter your password:");
  
    if (User === "hello" && Pass === "world") {        
      alert("Welcome.");
      break;
    
    } else if(attemptsRemaining <= 1) {          
      alert("To many failed attempts. Your account is now blocked.");
    }
    else {    
      alert("Incorrect username and/or password. You have " + (attemptsRemaining - 1) + " attempt(s) left."); 
    }
  }
}

这里的想法是添加额外的检查以查看attemptsRemaining 的数量是否已达到一个（或更少，为了稳健性），此时所有尝试都已过期。在这种情况下，您会显示一个弹出窗口，通知用户他们的帐户现在已被阻止。

希望有帮助！

【讨论】：