使用JavaScript从输入中读取数字始终返回NaN [英] Reading numbers from inputs with JavaScript always returns NaN

问题描述

我想创建一个简单地将2个字段相加的计算器。但无论我尝试什么它都行不通。如果我使用parseInt（），它也会返回NaN。

I want to create a calculator which simply sums 2 fields up. But whatever I try it does not work. It also returns "NaN", also if I use parseInt().

这是代码：

 <script type="text/javascript" language="Javascript">
 function doSum() 
 {
 var a = document.getElementsByName("a").value;
 var b = document.getElementsByName("b").value;

 var sum =  a + b;

 document.getElementById("sum").value = sum;
}
</script>

<form action="" method="POST">
<br/>a:<br/>
<input type="text" name="a" onblur='doSum()' value="0" size="5" />
<br/>b:<br/>
<input type="text" name="b" onblur='doSum()' value="0" size="5" />
<br/>Ergebnis<br/>
<input type="text" id='sum' value='' size="50" disabled/>
</form>

对不起那个菜鸟问题，但是我做错了什么？
感谢您的帮助！

Sorry for that noob question, but what I'am doing wrong? Thanks for any help!

推荐答案

提供 id s输入并使用 document.getElementById 唯一地识别它们。然后，使用<$ href =https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/parseInt，使用 parseInt 获取其十进制int值=noreferrer>基数参数设置为10并显示当前的结果。

Give ids to your inputs and identify them uniquely using document.getElementById. Then, obtain their decimal int values using parseInt with the radix parameter set to 10 and display the result as you currently do.

<script type="text/javascript" language="Javascript">
 function doSum() 
 {
  var a = parseInt(document.getElementById("a").value, 10);
  var b = parseInt(document.getElementById("b").value, 10);

  var sum =  a + b;

  document.getElementById("sum").value = sum;
}
</script>

<form action="" method="POST">
 <br/>a:<br/>
<input type="text" id="a" onblur='doSum()' value="0" size="5" />
 <br/>b:<br/>
<input type="text" id="b" onblur='doSum()' value="0" size="5" />
 <br/>Ergebnis<br/>
<input type="text" id='sum' value='' size="50" disabled/>
</form>

getElementsByName 返回元素列表和你即使列表只包含一个元素，也必须通过索引引用你想要的那个。

getElementsByName returns a list of elements and you'd have to refer to the one you want through an index, even if the list contains only one element.

getElementById 另一方面，通过其id返回唯一标识的元素。

getElementById on the other hand, returns an uniquely identified element, by its id.

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