使用定点 Using Heregexes

问题 Problem

你需要编写一个复杂的正则表达式。

You need to write a complex regular expression.

方法 Solution

使用CoffeeScript的“顶点”——对正则表达式进行了扩展，可以忽略正则中的空格，还可以包含注释。

Use Coffeescript’s “heregexes” – extended regular expressions that ignore internal whitespace and can contain comments.

pattern = ///
  ^\(?(\d{3})\)? # Capture area code, ignore optional parens
  [-\s]?(\d{3})  # Capture prefix, ignore optional dash or space
  -?(\d{4})      # Capture line-number, ignore optional dash
///
[area_code, prefix, line] = "(555)123-4567".match(pattern)[1..3]
# => ['555', '123', '4567']

讨论 Discussion

把你的正则表达式分割开，并给关键的部分添加注释，可以让正则表达式更容易理解和维护。例如，改变这个正则，使得前缀和line-number之间可以有空格，就很明显了。

Breaking up your complex regular expressions and commenting key sections makes them a lot more decipherable and maintainable. For example, changing this regex to allow an optional space between the prefix and line number would now be fairly obvious.

在顶点总的空字符 Whitespace characters in heregexes

既然空格符在heregexes中被省略掉了，那如果你需要匹配一个字面的ASCII空格该怎么办呢？

Whitespace is ignored in heregexes – so what do you do if you need to match a literal ASCII space?

一种方法就是使用@\s@这个字符类，它可以匹配空格、tab和换行。如果你只想匹配一个空格，那就需要使用\x20来表示一个字面的ASCII空格符。

One solution is to use the @\s@ character class, which will match spaces, tabs and line breaks. If you only want to match a space, though, you’ll need to use \x20 to denote a literal ASCII space.