Javascript 数学返回 NaN

Question

我的数学似乎都是正确的，但我返回的是 NaN。

Javascript:

// This section calculates how much the user will have to spend until the average age of life expectancy.
function updatespending() {
  var age = parseFloat(document.forms[0].CurrentAge.value);
  var value = parseFloat(document.forms[0].NetWorth.value);
  if(document.forms[0].sex.value == "male")
     {var yearsleft = Math.round (76 - age);}
  else if(document.forms[0].sex.value == "female") 
     {var yearsleft = 81 - age;}
  document.forms[0].AnnualSpending.value = Math.round (value / years left);

HTML 代码:

<table width="433" border="1" align="center">
  <tr>
    <td class="liquidate">How much will you have to live off of if you liquidate all of your assets?</td>
    </tr>
  <tr>
    <td width="381" height="68"><table width="100%" border="0" cellpadding="4" cellspacing="4">
      <tr>
        <td align="right">Sex:</td>
        <td>
        <input type="radio" name="sex" value="male">Male<br>
        <input type="radio" name="sex" value="female">Female
        </td>
      </tr>
      <tr>
        <td align="right">Current Age:</td>
        <td><input type="text" onchange="updatespending()" onkeyup="numericOnly(this)" maxlength="2" size="3" value="0" name="CurrentAge" /></td>
      </tr>
      <tr>
        <td align="right" >Annual Spending Available:</td>
        <td>$<input name="AnnualSpending" disabled="disabled" readonly /></td>
      </tr>
    </table></td>
  </tr>
</table>

当然，这一切都包含在一种形式中。如果我删除 == 并放置 = ，它将返回第一个 if 语句所说的内容。其他任何值都会返回 NaN。任何帮助将不胜感激。

Answer 1

在你的最后一行你有:

document.forms[0].AnnualSpending.value = Math.round (value / years left);

不应该是:

document.forms[0].AnnualSpending.value = Math.round (value / yearsleft);

注意yearsLeft变量。