为什么“valueAsNumber"返回 NaN 作为值? [英] Why does 'valueAsNumber' return NaN as a value?
问题描述
在下面的代码中，我试图调用 valueAsNumber 但我只得到一个 NaN 返回.当我使用 parseInt 时，我得到了我期望的结果.这是为什么呢?
In the code below, I am trying to call valueAsNumber but I just get a NaN returned. When I use parseInt I get the result I expect. Why Is this?
<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>
推荐答案
考虑到属性名称，您的期望是合理的，但阅读实际 规格/文档:
Your expectations are reasonable considering the property name, but reading actual specs/documentation:
valueAsNumber IDL 属性表示元素的值，解释为数字.
The valueAsNumber IDL attribute represents the value of the element, interpreted as a number.
获取时，如果 valueAsNumber 属性不适用，如定义对于输入元素的类型属性的当前状态，然后返回一个非数字 (NaN) 值.
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.
这是一个表格，它列出了适用于 valueAsNumber 的 type.它们是:
Here's a table that list's types that apply to valueAsNumber. These are:
- 日期和时间 (
datetime)(请注意，此type=""现在在 HTML LS 中已过时) - 日期(
日期) - 月(
月) - 周(
周) - 时间(
时间) - 本地日期和时间 (
datetime-local) - 编号(
编号) - 范围(
范围)
- Date and Time (
datetime) (Note thistype=""is now obsolete in HTML LS) - Date (
date) - Month (
month) - Week (
week) - Time (
time) - Local Date and Time (
datetime-local) - Number (
number) - Range (
range)
观察到 type="text" 明显不在上述列表中，因此 textInput.valueAsNumber 将始终返回 NaN 即使 isNaN( parseInt( textInput.value, 10 ) ) === false.
Observe that type="text" is conspicuously absent from the above list, therefore textInput.valueAsNumber will always return NaN even when isNaN( parseInt( textInput.value, 10 ) ) === false.
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