问题描述
我正在使用javascript验证器，它可以让我根据regexp构建自定义验证
I am using a javascript validator which will let me build custom validation based on regexp
从他们的网站： regexp = ^ [A- Za-z] {1,20} $ 允许最多20个字母字符。
From their website: regexp=^[A-Za-z]{1,20}$ allow up to 20 alphabetic characters.
如果输入的数据在输入字段超出此范围。
This will return an error if the entered data in the input field is outside this scope.
如果值的第一个字符为asterix，则需要的是触发输入字段错误的字符串。
What I need is the string that will trigger an error for the inputfield if the value has an asterix as the first character.
我可以通过以下方式触发相反的操作（如果第一个字符不是星号则出错）
I can make it trigger the opposite (an error if the first character is NOT an asterix) with:
regexp=[\u002A]
Heeeeelp please :-D
Heeeeelp please :-D
推荐答案
怎么样：
^[^\*]
哪个匹配任何不的输入从星号开始;从示例正则表达式判断，任何与正则表达式不匹配的输入都将导致验证错误，因此使用双重否定您应该得到您想要的行为： - ）
Which matches any input that does not start with an asterisk; judging from the example regex, any input which does not match the regex will be cause a validation error, so with the double negative you should get the behaviour you want :-)
我的正则表达式的解释：
Explanation of my regex:
- 第一个
^表示在开始时字符串 -
[...]构造是一个字符class，括在括号中的单个字符 - 字符类开头的
^表示否定字符类，即匹配不列出的字符之一 -
\ *表示文字*;*在正则表达式中有特殊含义，所以我用反斜杠转义它。正如Rob在评论中指出的那样，在角色类中逃避（大多数）特殊字符并不是绝对必要的
- The first
^means "at the start of the string" - The
[...]construct is a character class, which matches a single character among the ones enclosed within the brackets - The
^in the beginning of the character class means "negate the character class", i.e. match any character that's not one of the ones listed - The
\*means a literal*;*has a special meaning in regular expressions, so I've escaped it with a backslash. As Rob has pointed out in the comments, it's not strictly necessary to escape (most) special characters within a character class
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