Node.js · Senior · Question 11 of 75

What is a typical cause of a slow regular expression blocking a Node.js server (ReDoS)?

/^(a+)+$/.test("aaaaaaaaaaaaaaaaaaaaaaaaaaaa!");

1Regular expressions always run on the thread pool and exhaust it
2The test method is deprecated
✓Correct answer: Nested quantifiers cause catastrophic backtracking, so matching takes exponential time on certain inputs

Explanation

Since the regex runs on the main thread, one request can freeze the whole server. Avoid nested quantifiers, limit input length, or use a linear-time engine like RE2.

What is a typical cause of a slow regular expression blocking a Node.js server (ReDoS)?

Explanation

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