regexDollarEscapes

Reports replacement strings with unescaped $ that should use $$.

✅ This rule is included in the ts stylistic and stylisticStrict presets.

Enforces escaping the $ character as $$ when using it literally in the replacement argument of String.prototype.replace() and String.prototype.replaceAll().

In these methods, $ has special meaning for substitution patterns like $& (matched substring), $1 (first capture group), etc. An unescaped $ followed by an unrecognized character will be treated as a literal $, but this behavior is confusing and error-prone.

This rule reports unescaped $ characters in replacement strings that are not valid substitution pattern matchers.

Examples

Unescaped Dollar Sign

❌ Incorrect

const result = "€100".replace(/€/, "$");

✅ Correct

const result = "€100".replace(/€/, "$$");

Dollar Before Invalid Substitution Character

❌ Incorrect

const result = "abc".replace(/./, "$x");

✅ Correct

const result = "abc".replace(/./, "$$x");

Valid Substitution Patterns

✅ Correct

const matchedSubstring = "abc".replace(/./, "$&");
const firstGroup = "abc".replace(/(.)/, "$1");
const namedGroup = "abc".replace(/(?<char>.)/, "$<char>");
const literalDollar = "abc".replace(/./, "$$");

Options

This rule is not configurable.

When Not To Use It

If you intentionally rely on the behavior where $ followed by an unrecognized character produces a literal $, you might prefer to disable this rule.

Further Reading

• MDN: String.prototype.replace()
• MDN: String.prototype.replaceAll()

Equivalents in Other Linters

• ESLint: regexp/prefer-escape-replacement-dollar-char