用于在JavaScript中查找Java格式字符串的正则表达式

Question

In Java/Android, you can use Format strings to specify how some outlook is expected to look like. These Format strings can be passed to String.format() or Formatter() , for example.

Simple examples are %s or %1$d .

Now I would like to write a RegEx that works in JavaScript and lets you extract Java's format strings from a given text.

My solution would be the following RegEx:

%(([0-9]+\$)?)([,+ (\-#0]*)([0-9]*)(.[0-9]*)((hh|h|l|ll|L|z|j|t)*)(d|i|u|f|F|e|E|g|G|x|X|o|s|S|c|C|a|A|b|B|h|H|p|n|%)

However, this does not even work for the easiest case ( %s ). But it seems to work for all other (more complex) cases.

What I'm asking here is: Would you say this is a good (correct) RegEx or is anything missing?

My sources for the syntax have been: Android's Formatter class and printf format strings

Answer 1

The problem lies in this group: (.[0-9]*)

You expect a % at first then the . in the above group is expecting one of something (not optional). Then (d|i|u|f|F|e|E|g|G|x|X|o|s|S|c|C|a|A|b|B|h|H|p|n|%) is also expecting something.

So basically the only required items in your regex are:
1. %
2. the . in (.[0-9]*)
3. (d|i|u|f|F|e|E|g|G|x|X|o|s|S|c|C|a|A|b|B|h|H|p|n|%)

There isn't room in %s to accommodate the % and both the . and the chunk you are wanting to pull the s .

I'm not sure exactly what you want (.[0-9]*) to be, but making it optional like (.[0-9]*)? would atleast allow for %s to pass.