Match only the last instance of a regex that I only know partially

I want to match just the last instance of a regular expression. For example in this string:

some text here foo word bar and foo word foo word foo word bar more text here

I am trying to only match the bolded portion. Here is what I have tried currently:

 /foo?.+?bar/gi

However, it is keeping all of the italicized portion. What am I doing wrong?

>Solution :

You may use this regex that matches closes foo...bar pair without allowing any foo or bar in the middle:

foo(?:(?!foo|bar).)+bar(?!.*foo.+bar)

RegEx Demo 1

RegEx Details:

• foo: Match foo
• (?:(?!foo|bar).)+: Match 1+ of any character as long as it is not immediately followed by a foo or bar.
• bar: Match bar
• (?!.*foo.+bar): Make sure we don’t have any foo..bar match on RHS

If you are fine with getting your match in a capture group then consider this more efficient version of regex:

.*(foo(?:(?!foo|bar).)+bar)

RegEx Demo 2