Quick Fix: When using the v flag with a regular expression, remember to always escape literal hyphens inside character classes. This is because the v flag applies more restrictions to escaping rules, and an unescaped hyphen at the end of a character class is now considered an error.
The Solutions:
Solution 1: Using RegExp `v` Flag
The `v` flag in regular expressions was introduced to enhance Unicode support and enable character class subtraction and intersection. However, this flag also imposes stricter escaping rules.
In your regex pattern, `^[a-zA-Z0-9+_.-]+@[a-zA-Z0-9]+\.[a-zA-Z0-9]+$`, the literal hyphen (-) at the end of the character class `[a-zA-Z0-9+_.-]` is not escaped. Under the `v` flag, this unescaped hyphen is treated as a special character and causes the pattern to be invalid.
To resolve the issue, escape the hyphen with a backslash (\) to indicate that it should be treated as a literal character:
/^[a-zA-Z0-9+_.-]+@[a-zA-Z0-9]+\.[a-zA-Z0-9]+$/v
Alternatively, you can use the `u` flag instead of the `v` flag. The `u` flag also supports Unicode but does not enforce the stricter escaping rules:
/^[a-zA-Z0-9+_.-]+@[a-zA-Z0-9]+\.[a-zA-Z0-9]+$/u
Q&A
Why is my Regex valid with the u flag, but not with the v flag and does not work in pattern attribute with error: ‘Invalid character in character class
—
Use the u flag, there is no such a restriction, with the v flag, it is in place. So, escape literal hyphens inside character classes in ECMAScript patterns
Video Explanation:
The following video, titled "Having trouble with a regex inside the HTML pattern attribute ...", provides additional insights and in-depth exploration related to the topics discussed in this post.
my StackOverflow answer: - Valid with the RegExp u flag, but not with the v flag: https://stackoverflow.com/a/76287241/3832970 And also ...
