regexOctalEscapes

Reports octal escape sequences in regular expressions.

✅ This rule is included in the ts logical and logicalStrict presets.

Reports octal escape sequences in regular expressions. Octal escapes like \7 or \07 can be confused with backreferences. The same sequence (e.g., \2) may be a character or a backreference depending on the number of capturing groups in the pattern.

Examples

Octal Escape Starting with Zero

❌ Incorrect

const pattern = /\07/;
Error ts(1487)  ― Octal escape sequences are not allowed. Use the syntax '\x07'.

✅ Correct

const pattern = /\x07/;

Simple Octal Escape

❌ Incorrect

const pattern = /\7/;
Error ts(1534)  ― This backreference refers to a group that does not exist. There are no capturing groups in this regular expression.

✅ Correct

const pattern = /\x07/;

Ambiguous Octal vs Backreference

❌ Incorrect

const pattern = /\1\2/;
Error ts(1534)  ― This backreference refers to a group that does not exist. There are no capturing groups in this regular expression.
Error ts(1534)  ― This backreference refers to a group that does not exist. There are no capturing groups in this regular expression.

✅ Correct

const pattern = /\x01\x02/;

In the incorrect example, \1 and \2 are octal escapes (matching characters with code 1 and 2). If capturing groups are added later, they could become backreferences.

Options

This rule is not configurable.

When Not To Use It

If you intentionally use octal escapes for specific character matching and understand the distinction from backreferences, you might want to disable this rule. Octal escapes inside character class ranges (e.g., [\1-\4]) are allowed.

Further Reading

• MDN: Character escape
• MDN: Backreference

Equivalents in Other Linters

• ESLint: regexp/no-octal