javascript - 为什么这个简单的 JavaScript 程序不能运行？

Question

警报窗口向我显示消息 NaN 出了什么问题？感谢您的帮助

var weight = parseFloat(document.BMI.weight.value)
var height = parseFloat(document.BMI.height.value)

function calcBMI() {
var answer = weight * 703 / (height*height)
return answer;
  }
    </script>


 <form action="" name="BMI">
<input type="text" name="weight" />
<input type="text" name="height" />
<input type="submit" onclick="alert(calcBMI())" />
</form>

Answer 1

<script type="text/javascript">
function calcBMI() {
var weight = parseFloat(document.BMI.weight.value)
var height = parseFloat(document.BMI.height.value)
var answer = weight * 703 / (height*height)
return answer;
  }
    </script>


 <form action="" name="BMI">
<input type="text" name="weight" />
<input type="text" name="height" />
<input type="submit" onclick="alert(calcBMI())" />
</form>

希望它现在可以工作:)