RegEx find all matches not present in the following set

Question

How to perform a regex replace on the dot symbol that is not present within a specific match (for example in an image HTML tag)

str = "Hi. the symbol before me is my match target <img src='http://skip.these.dots/and.this.as.well' alt='me.three' /> but still match this."

To be replaced with (for example) * symbol

res = "Hi* the symbol before me is my match target <img src='http://skip.these.dots/and.this.as.well' alt='me.three' /> but still match this*"

Answer 1

Try this:

\.(?![^<]*\/>)

Demo

The regex engine performs the following operations.

\.      # match period
(?!     # begin negative lookahead
  [^<]* # match 0+ chars other than '<'
  \/>   # match '/>'
)

The negative lookahead fails if it encounters /> after the period without any intervening <, meaning the period must be between a < and an />.

You wish to replace each match of a period with *. How you do that depends on the language you are using, but it is undoubtedly straightforward.