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Update support note in 9.15 (Catastrophic backtracking)

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Refs: https://bugs.chromium.org/p/v8/issues/detail?id=10765
Refs: https://bugs.chromium.org/p/v8/issues/detail?id=11021

Can be tested in the Goole Chrome Beta, Dev, and Canary branches now,
as well as in the Node.js v8-canary branch.
This commit is contained in:
Vse Mozhe Buty 2020-12-10 16:59:05 +02:00
parent 633db6fbe9
commit 4512a02fd0
1 changed files with 4 additions and 4 deletions
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8
9-regular-expressions/15-regexp-catastrophic-backtracking/article.md
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@ -37,7 +37,7 @@ let str = "An input string that takes a long time or even makes this regexp hang
alert( regexp.test(str) );
```
To be fair, let's note that some regular expression engines can handle such a search effectively. But most of them can't. Browser engines usually hang.
To be fair, let's note that some regular expression engines can handle such a search effectively. But most of them can't. Browser engines usually hang (Google Chrome can handle such a search since version 88 due to a new experimental regular expression engine shipped in V8, JavaScript engine for browsers and Node.js).
## Simplified example
@ -74,7 +74,7 @@ Here's what the regexp engine does:
```
After all digits are consumed, `pattern:\d+` is considered found (as `match:123456789`).
Then the star quantifier `pattern:(\d+)*` applies. But there are no more digits in the text, so the star doesn't give anything.
The next character in the pattern is the string end `pattern:$`. But in the text we have `subject:z` instead, so there's no match:
@ -220,7 +220,7 @@ The time needed to try a lot of (actually most of) combinations is now saved.
## Preventing backtracking
It's not always convenient to rewrite a regexp though. In the example above it was easy, but it's not always obvious how to do it.
It's not always convenient to rewrite a regexp though. In the example above it was easy, but it's not always obvious how to do it.
Besides, a rewritten regexp is usually more complex, and that's not good. Regexps are complex enough without extra efforts.
@ -246,7 +246,7 @@ Possessive quantifiers are in fact simpler than "regular" ones. They just match
There are also so-called "atomic capturing groups" - a way to disable backtracking inside parentheses.
...But the bad news is that, unfortunately, in JavaScript they are not supported.
...But the bad news is that, unfortunately, in JavaScript they are not supported.
We can emulate them though using a "lookahead transform".