JavaScript正则表达式数字与包含单个零的字符串不匹配
[英]JavaScript Regular Expression digits not matching string containing single zero
问题描述
I'm using the JavaScript regular expression: 
我正在使用JavaScript正则表达式：
val.match(/\d*$/)
It works as expected for all numbers expect when the string is "0". 对于字符串为“ 0”时预期的所有数字，它均按预期方式工作。 A single zero value does not match. 单个零值不匹配。 How do I include that? 如何包括在内？
Test case: 测试用例：
<html>
<head>
<script src="scripts/jquery-1.5.1.min.js" type="text/javascript"></script>
</head>
<body>
<input type="text" id="txtRange" />
<div id="result" />
<script type="text/javascript">
var rangeValidate = function (val, min, max) {
if (val == "") {
return "You must specify a number between " + min + " and " + max;
} else if (val.match(/\d*$/) == false) {
return "You must specify a number between " + min + " and " + max;
} else if ((val < min) || (val > max)) {
return "You must specify a number between " + min + " and " + max;
} else {
return "";
}
return "You must specify a number between " + min + " and " + max;
}
$('#txtRange').bind('change', function(){
var value = $('#txtRange').val();
var resultText = rangeValidate(value, 0, 8);
$('#result').html(resultText);
});
</script>
</body>
</html>
4 个解决方案
解决方案1
4 已采纳 2011-03-23 18:41:50
It matches, "0".match(/\\d*$/) returns the array ["0"] which when used in comparison is converted to its string representation "0" . 它匹配"0".match(/\\d*$/)返回数组["0"] ，在比较中将其转换为字符串表示形式"0" 。
但是在JavaScript中，字符串“ 0”是“ falsy”，这意味着它在布尔上下文中的值为false。 Edit: Ok, the string is not "falsy". 编辑：好的，字符串不是“ falsy”。 Still, there is some conversion going on which eventually has the effect that "0" == false evaluates to true . 仍然有一些正在进行的转换，最终导致"0" == false评估为true 。
You should use .test() [docs] (which always returns a boolean value) instead and/or strict equality === : 您应该改用.test() [docs] （始终返回布尔值）和/或严格等于=== ：
} else if (/\d*$/.test(val) === false) {
If the whole string should be a number, you should also anchor the expression at the beginning of the string: 如果整个字符串应为数字，则还应将表达式锚定在字符串的开头：
/^\d*$/
Or don't use regex at all and use + to convert the value to a number. 或者根本不使用正则表达式，而使用+将值转换为数字。 If it cannot be converted (because it contains something else than digits) it will return the special value NaN (not a number). 如果它不能转换（因为它包含数字以外的东西），它将返回特殊值NaN （不是数字）。 You're code would become: 您的代码将变成：
var rangeValidate = function (val, min, max) {
val = +val;
if (isNaN(val) || (val < min) || (val > max)) {
return "You must specify a number between " + min + " and " + max;
} else {
return "";
}
}
解决方案2
1 2011-03-23 18:40:23
Okay, wow... just weird. 好吧，哇...真奇怪。 What's actually going on: 实际发生了什么：
The result from a .match is an array. .match的结果是一个数组。 Since you have a single match, your result is ['0'], and ['0'].toString() === '0' == false. 由于您只有一个匹配项，因此结果为['0']和['0']。toString（）==='0'== false。
In ANY other case (if you matched a paren set in the regex, etc), this would be NOT equal false regardless of whether or not it was zero. 在任何其他情况下（如果您匹配了正则表达式中设置的括号），则无论它是否为零，都将不等于false。
Now for the weird bit: 现在，奇怪的是：
> ['0'] == false
true
> !!['0']
true
So the == operator forces an implicit .toString() where as the ! 因此，==运算符会强制使用一个隐式.toString（），其中！ operator doesn't! 操作员没有！
解决方案3
1 2011-03-23 18:41:07
0 == false returns true in javascript. 0 == false在javascript中返回true。 0 === false will return false in javascript. 0 === false将在javascript中返回false。
Change your val.match(/\\d*$/) == false in val.match(/\\d*$/) === false . 在val.match(/\\d*$/) == false中更改您的val.match(/\\d*$/) == false val.match(/\\d*$/) === false 。 I don't know if this will fix your problem, but it's always good to keep this in mind. 我不知道这是否可以解决您的问题，但是牢记这一点总是很好的。
解决方案4
0 2011-03-23 19:09:46
Try this:- 尝试这个：-
var rangeValidate = function (val, min, max) {
if ( /^\d+$/.test(val) && val>=min && val<=max ) {
return "";
} else {
return "You must specify a number between " + min + " and " + max;
}
}
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