In this statement, for example, A => B we say that B is in front of A and A is behind B

  • A(? =B) Look ahead positive: matches A with B in front of A.

To match an expression ABC preceded by 123, it should look like this:

  • A(? ! B) Look ahead negative: As the name implies, this re matches A with the constraint that A is not preceded by B

To match ABC and ABC is not preceded by 123, it should look like this:

  • (? <=B) Look behind positive: match expression A, restrict condition A is followed by B

If you want to match ABC and ABC is followed by 123, embarrassingly, JS does not support backwardness, only backwardness, so using JS matches will look like this:

So I changed the Sublime editor, and since sublime is written in Python, I got something like this:

  • (?

To match ABC and ABC is not followed by 123, it should look like this:

Of course, negative backwardness is not supported in JS, but there seems to be a proposal to allow JS to support backwardness, I believe that a few years js can support backwardness.