regexSuperLinearMoves

Reports quantifiers that can cause quadratic regex matching time.

✅ This rule is included in the ts logical presets.

When a quantifier at the start of a pattern is followed by elements that can fail to match, the regex engine may try the pattern from each position in the input string. For an input of length n, this can result in O(n²) time complexity.

This rule reports quantifiers that can cause quadratic regex matching time.

Examples

Basic Quantifier with Literal Suffix

❌ Incorrect

const pattern = /a*b/;

✅ Correct

const pattern = /^a*b/;

Character Set Quantifier

❌ Incorrect

const pattern = /\s+foo/;

✅ Correct

const pattern = /^\s+foo/;

Quantifier Inside Group

❌ Incorrect

const pattern = /(?:\s*)foo/;

✅ Correct

const pattern = /^(?:\s*)foo/;

RegExp Constructor

❌ Incorrect

const pattern = new RegExp("a*b");

✅ Correct

const pattern = new RegExp("^a*b");

Options

This rule is not configurable.

When Not To Use It

If your regex is only used on small trusted inputs where performance is not a concern, you might want to disable this rule. Some patterns are inherently super-linear but necessary for the matching logic. You might consider using Flint disable comments and/or configuration file disables for specific cases instead of completely disabling this rule.

Further Reading

• MDN: Quantifier
• MDN: Assertions
• Regular Expression Denial of Service (ReDoS)

Equivalents in Other Linters

• ESLint: regexp/no-super-linear-move