Question

/}/ is a valid regular expression in JS:

alert('}}}'.replace(/}/g, "!"))

However, the ECMA standard doesn’t seem to allow that:

PatternCharacter ::SourceCharacter but not any of:
      ^ $ \ . * + ? ( ) [ ] { } |

Why does the above work? Is this feature universally supported? Is it documented anywhere?

Answer 1

http://www.regular-expressions.info/characters.html :

Most regular expression flavors treat the brace { as a literal
character, unless it is part of a repetition operator like {1,3}. So
you generally do not need to escape it with a backslash, though you
can do so if you want. An exception to this rule is the
java.util.regex package: it requires all literal braces to be escaped.

Seems that javascript is not an exception.