创建带有提示的网页

Question

我的提示框不起作用？自从我把元素的东西放进去之后，那里就不起作用了。

我需要提示框，以便我可以输入信息，然后该信息自动进入表格，然后通过在表格的行中有 * 来自动读取最大金额的 $。我不是 100% 的 js 编码，所以如果它是一个简单的解决方法，请不要笑（这是让我感兴趣的简单事情）。

这是我的代码，我不知道我做错了什么

“我的桌子在头上”

function money(){

this.currency = "";
this.amount = "";
this.exchangeRate = "";
this.ausDollars = "";

tbody = document.getElementsByTagName('tbody')[0];
for (var i = 0; i <= 3; i++) 
  trElement = document.createElement('tr');
  tbody.appendChild(trElement);

// Read the 3 letter currency abbreviation entered
  currency = prompt('Please enter a 3-letter currency abbreviation', +i, "");
  // If the input data is invalid ask the user to re-enter it
  while (currency.length != 3) {
    currency = prompt('Currency abbreviation was not entered', "");
    currency = parseFloat(currency);
  }

currencyTH = document.createElement('th');
  currencyText = document.createTextNode(currency);
  currencyTH.appendChild(currencyText);
  trElement.appendChild(currencyTH);

 // Read the amount and convert it to entered currency 
  amount = prompt('Please enter an amount of money in that currency', +i, "");
  // If the input data is invalid ask the user to re-enter it
  while (isNaN(amount) || amount < 0) {
    amount = prompt('An amount of money was not entered')
    amount = parseFloat(amount);
  }

amountTH = document.createElement('th');
  amountText = document.createTextNode(amount);
  amountTH.appendChild(amountText);
  trElement.appendChild(amountTH);

 exchangeRateTH = document.createElement('th');
  exchangeRateText = document.createTextNode(exchangeRate);
  exchangeRateTH.appendChild(exchangeRateText);
  trElement.appendChild(exchangeRateTH);

}

Answer 1

问题在于您使用 prompt() 来提示用户输入并显示与用户输入相关的错误消息。为此，您正在寻找 alert()。

首先您在提示中设置货币：

currency = prompt('Please enter a 3-letter currency abbreviation', +i, "");

然后你运行：

 currency = prompt('Currency abbreviation was not entered', "");

这覆盖最初存储在currency 中的值，因此您无法在下一行对其运行parseFloat()：

 currency = parseFloat(currency);

要解决此问题，请使用：

alert('Currency abbreviation was not entered');

请注意，amount 也是如此。而不是：

amount = prompt('An amount of money was not entered');

用途：

alert('An amount of money was not entered');

另请注意，您的while 循环结构在满足正确值之前无限期提示略有错误。您应该在循环之外设置一个变量，然后检查条件，而不是最初提示然后运行您的 while 循环。而parseFloat() 必须在while循环之外，否则你会陷入无限循环！

var currency = '';
currency = prompt("Please enter 3 characters");
while (currency.length != 3) {
  alert('Currency must be three characters');
  currency = prompt("Please enter 3 characters");
}
currency = parseFloat(currency);

console.log("The stored value was: " + currency);

希望这会有所帮助！ :)