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Merge pull request #886 from overken/patch-2

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Update article.md
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Ilya Kantor 2019-04-02 08:41:34 +03:00 • committed by GitHub
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5-regular-expressions/15-regexp-infinite-backtracking-problem/article.md
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@ -12,7 +12,7 @@ For server-side Javascript it may become a vulnerability, and it uses regular ex
So the problem is definitely worth to deal with. So the problem is definitely worth to deal with.
## Introductin ## Introduction
The plan will be like this: The plan will be like this:
@ -254,7 +254,7 @@ Unfortunately, but both these features are not supported by JavaScript.
### Lookahead to the rescue ### Lookahead to the rescue
We can get forbid backtracking using lookahead. We can forbid backtracking using lookahead.
The pattern to take as much repetitions as possible without backtracking is: `pattern:(?=(a+))\1`. The pattern to take as much repetitions as possible without backtracking is: `pattern:(?=(a+))\1`.
@ -274,7 +274,7 @@ Let's fix the regexp for a tag with attributes from the beginning of the chapter
```js run ```js run
// regexp to search name=value // regexp to search name=value
let reg = /(\s*\w+=(\w+|"[^"]*")\s*)/ let attrReg = /(\s*\w+=(\w+|"[^"]*")\s*)/
// use new RegExp to nicely insert its source into (?=(a+))\1 // use new RegExp to nicely insert its source into (?=(a+))\1
let fixedReg = new RegExp(`<\\w+(?=(${attrReg.source}*))\\1>`, 'g'); let fixedReg = new RegExp(`<\\w+(?=(${attrReg.source}*))\\1>`, 'g');