javascript parseInt is broken
javascript parseInt is broken
I was debugging some strange errors in a date conversion function I was writing, and I stumbled upon something that amazed me... a strange bug in parseInt
>>>parseInt('06')
6
>>>parseInt('07')
7
>>>parseInt('08')
0
>>>parseInt('09')
0
>>>parseFloat('08')
8
>>>parseFloat('09')
9
Clearly for the strings '08' and '09' parseInt fails to return the right value. One workaround is easy, use parseFloat.
Why does this happen and where should I report this? I find it extremely odd that it happens in both Firefox and Internet Explorer 6 & 7; there must be some explanation right?
You can test it out for yourself using the FireBug javascript console), or by using one of these two links
alert(parseInt('07')+' == 7 ?')
alert(parseInt('08')+' == 8 ?')
Ok, Ok, so now that I explained how you would expect it to work (and clearly how I expected it to work) I'm going to answer my own question (yes I hate it when I do that too)
The problem is with how parseInt guesses the base of your number. Read the parseInt spec. Instead of always defaulting to base 10, it tries to guess, and if the first character is '0' it thinks you want to parse as an octal number, and if it starts with '0x' it thinks you want hexadecimal.
So, the solution is either to use parseFloat or to always specify your base.
Defaults that change on their own can't be trusted.
>>>parseInt('08',10)
8
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先让我们来理解一个概念:
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那么我们很容易想到这个拥有者,必然有个终点,那就是window对象。
......
转载理由:短小精悍。
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只有一种值 undefined
以下三种情况typeof 返回类型为undefined
1. 当变量未初始化时
2. 变量未定义时
3. 函数无明确返回值时(函数没有返回值时返回的都是undefined)
undefined 并不等同于未定义的值
typeof 并不真正区分是否是未定义
看以下示例 ......
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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>无标题文档</title>
</head>
<mce:style><!--
.man{ float:left; background:#9af; margin:3px; padding:3px; cursor:default}
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//校验是否全由数字组成
function isDigit(s)
{
var patrn=/^[0-9]{1,20}$/;
if (!patrn.exec(s)) return false
return true
}
//校验登录名:只能输入5-20个以字母开头、可带数字、“_”、“.”的字串
Java代码
function isRegisterUserName(s)
......