如何编写正则表达式来检查JavaScript中有效的XML元素NCName？

Question

NCNam表示它必须以字母或下划线开头，并且只能包含字母，数字，下划线，连字符和句点。我试图这样写正则表达式，但我认为可能是错误的。

if(/^([_]|[a-zA-Z]+[\w\W])$/.test('abc' ))  console.log('match')

Answer 1

Your ^([_]|[a-zA-Z]+[\\w\\W])$ pattern matches a string that is either equal to _ ( [_] ) or ( | ) is formed of 1+ letters ( [a-zA-Z]+ ) followed with any char ( [\\w\\W] ). So, it cannot validate the strings of the type you mention.

You may use

/^[a-zA-Z_][\w.-]*$/

See the regex demo and the graph ( source ) below:

Details

• ^ - start of string
• [a-zA-Z_] - a letter or _
• [\\w.-]* - 0 or more letters, digits, underscores, dots or hyphens
• $ - end of string

Answer 2

must start with a letter or underscore

Match the first character with [a-z_]

and can only contain letters, digits, underscores, hyphens, and periods

Use a character class containing all of those. Note that letters, digits, and underscores together make up the representation of a "word character", so you can use \\w instead of writing those out separately.

In full:

/^[a-z_][\w.-]*$/i