如何使用Javascript正则表达式从可能单词的列表中获取单词的最后出现？

Question

I need to test if an address contains a particular placename from a list of placenames. For example, if I have an address that looks like 123 someplace, someStreet, dublin then the following regex (dublin|cork|galway) will give me county dublin .

The problem is if dublin was to appear in some other portion of the address eg 123 someplace, dublin road, cork then I'll still get dublin but I actually want cork .

Is it possible to write a regex to get the last occurrence, if any, of a list of possible match words. I see that C# regexes have a right-to-left option, that would be great but I don't think Javascript has anything like that, does it?

Note that I can't rely on the formatting of the address, so there might not be commas delimiting the string. Also, although it is very likely that the word I'm looking for is the very last word in the string, this might not always be the case.

Answer 1

You can use positive look ahead

(dublin|cork|galway)(?!.*(dublin|cork|galway))

matches the last occurence

see how the regex works

http://regex101.com/r/yQ6bY1/2

(?!.*(dublin|cork|galway)) asserts that the pattern cannot be matched after the presceding pattern, (dublin|cork|galway)

OR

To be more precise,

\b(dublin|cork|galway)\b(?!.*\b(dublin|cork|galway)\b)

Thanks to nhahtdh for the suggestion.

Answer 2

Find desired string and check that end of line does not contain it.

(dublin|cork|galway)(?!.*(dublin|cork|galway))

regex demo