CODEWITHSUNDEEP
phpregex
Jakub Truneček
Jakub Truneček

Reputation: 8990

What do ++ and *+ mean?

I am porting some libraries from PHP to JavaScript and I came across this regular expression, some parts of it are unclear to me.

#(?: *+(?<= |^)\.((?:\([^)\n]++\)|\[[^\]\n]++\]|\{[^}\n]++\}|<>|>|=|<){1,4}?))#

Unclear parts are

  1. *+
  2. ++

I know, that this expression should accept strings like

.(title)[class]{style}<>
.[class]{style}<>
.[class](title){style}
// and so one - no metter of order \(.+\), \[.+\] and \{.+\} parts 
// and optional <>, >, = or < at the end

This expression is used with PCRE_UNGREEDY modifier.

Upvotes: 26

Views: 18151

Answers (1)

Wouter J
Wouter J

Reputation: 41934

++

From What is double plus in regular expressions?

That's a Possessive Quantifier.

It basically means that if the regex engine fails matching later, it will not go back and try to undo the matches it made here. In most cases, it allows the engine to fail much faster, and can give you some control where you need it - which is very rare for most uses.

*+

*+ is the possessive quantifier for the * quantifier.

Upvotes: 29

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