Question

不是RegEx的大用户 - 从未真正了解它们！但是，我觉得检查用户名字段输入的最佳方法是使用只允许字母（上部或下部），数字和_字符的输入，并且必须根据网站策略以字母开头。 My RegEx和代码是这样的：

var theCheck = /[a-zA-Z]|\d|_$/g;
alert(theCheck.test(theUsername));

尽管尝试了各种组合，但一切都回归“真实”。

有人可以帮忙吗？

Answer 1

你的正则表达式是说“theUsername包含字母，数字或以下划线结尾”。

请改为尝试：

var theCheck = /^[a-z]([a-z_\d]*)$/i; // the "i" is "ignore case"

这表示“theUsername以字母开头，只包含字母，数字或下划线”。

注意：我认为你不需要“g”，这意味着“所有匹配”。我们只想测试整个字符串。

Answer 2

这样的事情怎么样：

^([a-zA-Z][a-zA-Z0-9_]{3,})$

解释整个模式：

^ = Makes sure that the first pattern in brackets is at the beginning
() = puts the entire pattern in a group in case you need to pull it out and not just validate
a-zA-Z0-9_ = matches your character allowances
$ = Makes sure that this must be the entire line
{3,} = Makes sure there are a minimum of 3 characters. 
    You can add a number after the comma for a character limit max
    You could also use a +, which would merely enforce at least one character match the second pattern. A * would not enforce any lengths

Answer 3

将此作为你的正则表达式：

^[A-Za-z][a-zA-Z0-9_]*$

Javascript RegEx没有按预期返回false

3 个答案: