javascript 为什么“valueAsNumber”将 NaN 作为值返回？
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Why does 'valueAsNumber' return NaN as a value?
提问by Avery
In the code below, I am trying to call valueAsNumberbut I just get a NaN returned. When I use parseIntI get the result I expect. Why Is this?
在下面的代码中，我试图打电话，valueAsNumber但我只是得到一个 NaN 返回。当我使用时，parseInt我得到了我期望的结果。为什么是这样？
<html>
<head>
<title>JavaScript: Demo 1</title>
<link rel="stylesheet" type="text/css" href="index.css">
</head>
<body>
<div id="numbers">
<div id="inputs">
<form name="inputForm">
<div class="prompt">Number 1: <input name="number1" type="text"></div>
<div class="prompt">Number 2: <input name="number2" type="text"></div>
</form>
</div>
<div id="result">
<div class="prompt">RESULT: <span id="operation_result"> </span></div>
</div>
</div>
<div id="operations">
<p><a id="add_link" href="#" onClick="add(this)">ADD</a></p>
</div>
<script type="text/javascript">
function add(linkElement){
// var value1 = parseInt(document.inputForm.number1.value);
// var value2 = parseInt(document.inputForm.number2.value);
var value1 = document.inputForm.number1.valueAsNumber;
var value2 = document.inputForm.number2.valueAsNumber;
var result = value1 + value1;
document.getElementById('operation_result').innerHTML = result;
}
</script>
</body>
</html>
回答by Esailija
Your expectations are reasonable considering the property name, but reading actual specs/documentation:
考虑到属性名称，您的期望是合理的，但请阅读实际的规范/文档：
The valueAsNumber IDL attribute represents the value of the element, interpreted as a number.
On getting, if the valueAsNumber attribute does not apply, as defined for the input element's type attribute's current state, then return a Not-a-Number (NaN) value.
valueAsNumber IDL 属性表示元素的值，解释为数字。
获取时，如果 valueAsNumber 属性不适用，如为输入元素的 type 属性的当前状态定义的，则返回一个非数字 (NaN) 值。
Here's a tablethat list's types that apply to valueAsNumber. These are:
这是一个表格，其中列出type了适用于的s valueAsNumber。这些是：
Date and Time,
Date,
Month,
Week,
Time
Local Date and Time,
Number
Range
日期和时间、
日期、
月、
周、
时间
本地日期和时间、
数字
范围
Yeah that's pretty weird API decision
是的，这是非常奇怪的 API 决定
回答by Joseph Silber
You have to set the typeof your inputto number:
你必须设置type你的input到number：
<input name="number1" type="number">
Also, if the value is empty or non-numeric, it'll return NaN.
此外，如果该值为空或非数字，它将返回NaN.
