Javascript regexp - 仅当第一个字符不是星号时 [英] Javascript regexp - only if first character is not an asterisk

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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