如何在javascript中正确嵌套while和for循环答案

【问题标题】：How do I properly nest while and for loops in javascript如何在javascript中正确嵌套while和for循环
【发布时间】：2014-03-14 01:05:54
【问题描述】：

刚刚学习 javascript 并且很难使用此代码，希望让它重复 5 次不同的随机数学问题，但只有在回答正确的情况下才能继续下一个问题。有人可以帮我指出正确的方向吗？

// var initialization
var num1 = Math.floor(Math.random()*100)+1;
var num2 = Math.floor(Math.random()*100)+1;
var correct = num1 + num2;
var guess = 0;
var count = 1;
var msg = " ";
//var debug = 5;

// loop basic math process

while(count <= 1){

guess = eval(prompt("What is "+num1+" + "+num2+" = __ ?"));

    if(guess != correct){
        msg = alert("Sorry please try again");

    }else{
        msg = alert("By George I think you got it!");

        for(i=0;i<=5;i+=1){
            alert(debug);
            var num1 = Math.floor(Math.random()*100)+1;
            var num2 = Math.floor(Math.random()*100)+1;
            var correct = num1 + num2;

            guess = eval(prompt("What is "+num1+" + "+num2+" = __ ?"));

        if(guess != correct){
            alert("Sorry please try again");

        }else{
            alert("Great your on a roll!");

        }}} count++;
}

【问题讨论】：

将count++ 放在else 条件中alert('Great you're on a roll!) 之后。
感谢您的快速回复。
使用console.log()作为调试输出；它远远优于警报（可以在一个好的浏览器中直接显示项目、元素等，而不仅仅是可怕的Object [object]。就此而言，也可以使用错误控制台查看错误消息！您发布的代码运行良好 - 如只要我修复了alert(debug)，它会在 chrome 中引发错误。
eval 应该像瘟疫一样被避免，直到你有足够的经验来聪明地反对那个立场。如以下示例所示，您根本不需要评估 prompt() 的结果。您的代码具有评估我在答案中输入的任何表达式的有趣副作用 - 最有趣的是，如果它问我总和是多少，我可以直接输入 12 + 45，它会评估加法，我什至没有做数学！你几乎从来没有，几乎从来不需要eval。

标签： javascript if-statement for-loop while-loop

【解决方案1】：

如果您想继续提问直到他们回答正确，那么您将需要两个循环。一算5题。其中一个是不断提出问题，直到它是正确的，我认为你的循环有点倒置。我会改为执行以下操作：

for(i=0;i<=5;i+=1){
    alert(debug);
    var num1 = Math.floor(Math.random()*100)+1;
    var num2 = Math.floor(Math.random()*100)+1;
    var correct = num1 + num2;
    var guess = -1;

    while (guess != correct) {    
        guess = eval(prompt("What is "+num1+" + "+num2+" = __ ?"));
        if(guess != correct){
            msg = alert("Sorry please try again");
        }else{
            msg = alert("By George I think you got it!");
        }
    }
}

如果您想知道他们是否连续多次正确更改消息，您必须检测他们是否处于连续状态：

var streak = 0;


    while (guess != correct) {    
        guess = eval(prompt("What is "+num1+" + "+num2+" = __ ?"));
        if(guess != correct){
            msg = alert("Sorry please try again");
            streak = 0;
        }else{
            streak++;
            if (streak < 2) {
                msg = alert("By George I think you got it!");
            } else {
                msg = alert("Keep up the good work!");
            }
        }
    }

【讨论】：

【解决方案2】：

根据您的编码，我想您不需要外部 while 循环。如果您确实需要 while 循环来控制 for 循环的总轮数，则最好将整个 for 循环代码包装在一个单独的函数中。

【讨论】：

【解决方案3】：

作为一个提示——如果你的编辑器没有能力重新格式化/重新缩进源代码，jsbeautifer.org 做得很好。

var num1;
var num2;
var guess;
var correct;
var msg;

// Bonus
// It looked like you were trying to give different responses so it wasn't 
// quite as boring

var successMessages = [
  "Way to go!",
  "Alright!",
  "Cheers!",
  "Tally ho!"
  "Well done, old boy"
];

var questionsLeft = 5;

// loop basic math process
while (questionsLeft !== 0) {

  num1 = Math.floor(Math.random() * 100) + 1;
  num2 = Math.floor(Math.random() * 100) + 1;
  correct = num1 + num2;

  guess = prompt("What is " + num1 + " + " + num2 + " = __ ? ");
  guess = parseInt(guess, 10); // Convert to a number

  if (guess !== correct) {
    msg = alert("Sorry please try again ");
  } else {
    msg = successMessages[questionsLeft];
    questionsLeft--;
  }
}

或者，如果你想让他们重复这个问题：

var num1;
var num2;
var guess;
var correct;
var msg;
var isRight;

// Bonus
// It looked like you were trying to give different responses so it wasn't 
// quite as boring

var successMessages = [
  "Way to go!",
  "Alright!",
  "Cheers!",
  "Tally ho!"
  "Well done, old boy"
];

var questionsLeft = 5;

// loop basic math process
while (questionsLeft !== 0) {

  num1 = Math.floor(Math.random() * 100) + 1;
  num2 = Math.floor(Math.random() * 100) + 1;
  correct = num1 + num2;

  // They haven't answered yet, so they can't be right.
  isRight = false;

  while (!isRight) {
    guess = prompt("What is " + num1 + " + " + num2 + " = __ ? ");
    guess = parseInt(guess, 10); // Convert to a number

    isRight = guess !== correct

    if (isRight) {
      msg = alert("Sorry please try again ");
    } else {
      msg = successMessages[questionsLeft];
      questionsLeft--;
    }
  }
}

【讨论】：

是的，我仍然熟悉 sublimetext 编辑器。感谢您的建议，下次我在这里发帖时，我会尝试 jsbeautifer.org。

【解决方案4】：

试试这个：

var num1 = [], num2 = [], correct = [], count = 0, guess;
for(var i=0; i<5; i++){
  num1[i] = Math.floor(Math.random()*101);
  num2[i] = Math.floor(Math.random()*101);
  correct[i] = num1[i]+num2[i];
}
while(count < 5){
  quess = prompt('What is '+num1[count]+'+'+num2[count]+' ?');
  if(+quess === correct[count]){
    alert('You are Correct!');
    if(++count === 5)alert('You Have Completed All of the Answers Correctly!!!');
  }
  else{
    alert('Please Try Again.')
  }
}

【讨论】：