javascript - Regular expression /(\d)(?=(\d{3})+\.)/gIf ?= is changed to ?: Why are the results different?

Question

I remember? :and? =Almost the same, but? : capture while? =Do not capture

Answer 1

I don’t know what your needs are. Judging from the title alone, there is not much difference

?=is positive lookahead ?:is not capturing

Answer 2

If you check whether it matches, then it will definitely return true, but if you take Full match, the two are different.

To understand the meaning of Lookahead, it matches a position, not the real character

Recommend a website for testing regex
https://regex101.com

Use the two regular expressions and 1333 tests you provided to separate the results