为什么JS方法replace（）在最新版本的Safari中工作不正确？

Question

Why does JS method replace() work incorrect in the latest version of Safari (11.1) with "$<" in the second argument?

Example:

"aaaXXXbbb".replace(/XXX/, '_before_$<_after_')

Actual result:

"aaa$<_after_bbb"

Expected result:

"aaa_before_$<_after_bbb"

PS: "$$" inserts a "$" and solves this problem

Answer 1

This behavior doesn't occur in Firefox or Chrome, and I think I understand why.

A new feature has been accepted for inclusion in the next version of the ECMAScript spec called 'Regex Named Capture Groups' which, as the name suggests, allows you to assign a name to a capture group in a regular expression. One of the things added by this feature is a new addition to the replacement string syntax which allows you to interpolate the value of a named capture group.

This syntax takes the form $<captureName> - note the $< at the beginning!

According to the latest iteration of the spec , if you haven't closed a $< with a corresponding > , it should be ignored and just treated as part of the text. The behavior being displayed in your browser doesn't line up with this, and therefore I think it's quite likely that you've discovered a bug!

I'd encoruage you to report it to WebKit via the process detailed on their website .