问题描述
基本上我有以下代码:
<input type="text" value="123" id="txtbox">
<script>
var myVar = document.getElementById('txtbox').value;
if (myVar.substring) {
alert('string');
} else{
alert('number');
}
</script>
无论您在文本框中输入什么值,它都会始终提醒字符串
。有没有办法,如果你在文本框中放一个数字,它会提醒数字
而不是字符串?谢谢。
No matter what value you put in the textbox, it will always alert string
. Is there a way that if you put a number in the textbox it will alert number
instead of string? Thank you.
推荐答案
值
on 输入
元素始终一个字符串。它可能是一串数字。
value
on input
elements is always a string. It might be a string of digits.
如果你想知道该字符串是否只包含有效数字,你必须解析它(并决定你认为什么是有效数字) ,并且允许那样)。
If you want to know whether that string only contains valid numbers, you have to parse it (and decide what you consider a valid number, and allow for that).
例如,你会让人们告诉你使用 parseInt(myVar)
或一元 +
( + myVar
)或 isNaN(myVar)
(其中一元 +
的确如此)或数字(myVar)
(相同),但:
For instance, you'll get people telling you to use parseInt(myVar)
or the unary +
(+myVar
) or isNaN(myVar)
(which does what the unary +
does) or Number(myVar)
(same), but:
-
parseInt
仅解析开头的字符串parseInt(345foo)
是345
parseInt
only parses the beginning of the string,parseInt("345foo")
is345
parseInt
当然只适用于整数;对于小数部分的数字你想要 parseFloat
parseInt
is, of course, only for whole numbers; you'd want parseFloat
for numbers with fractional portions
所有这些都无法理解成千上万的分隔符
All of those will fail to understand thousands separators
所有这些都无法理解不是的小数点分隔符。
(例如,许多语言环境是,
,有时甚至是空格)
All of those will fail to understand a decimal separator that isn't .
(e.g., in many locales it's ,
or sometimes even a space)
+ myVar
和 Number(myVar)
和 isNaN(myVar)
等会将空字符串视为 0
+myVar
and Number(myVar)
and isNaN(myVar)
and such will treat an empty string as 0
......那种事情。所以你必须根据你想接受的输入对字符串做一些准备。
...that kind of thing. So you have to do some prep on the string according to what input you want to accept.
一旦你决定要处理什么格式,就有一个这里有关于做实际解析的答案的十几个问题:
Once you've decide what format(s) to handle, there are a dozen questions with answers here about doing the actual parsing:
- (注意整数-specific)
- How do I Convert a String into an Integer in JavaScript? (note that's integer-specific)
- What's the fastest way to convert String to Number in JavaScript?
这篇关于检查文本框值是字符串还是javascript中的数字的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!