Skip to content
Flint
Blog

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

Section titled “Examples”

Octal Escape Starting with Zero

Section titled “Octal Escape Starting with Zero”
AEconsB0patteAE< =sp ansty="le--0:#5CA7E4;--1:#3A68">81<1/sp ansty="le--0:#F78C6C;--1:#AA09">82<\0sp ansty="le--0:#5CA7E4;--1:#3A68">81<1/sp ansty="le--0:#D6DEEB;--1:#403F">5<3;d ivclassNa="meco">
44AEco61B0pat446<88F spans="tyle--0:#D9F5DD;--1:#11">1<111/ spans="tyle--0:#F78C6C;--1:#AA">0982<\x07 spans="tyle--0:#D9F5DD;--1:#11">1<111/ spans="tyle--0:#D6DEEB;--1:#40">3<07/>

Simple Octal Escape

Section titled “Simple Octal Escape”
AEconsB0patteAE< =sp ansty="le--0:#5CA7E4;--1:#3A68">81<1/sp ansty="le--0:#5CA7E4;--1:#3A68">8F<\7sp ansty="le--0:#D9F5DD;--1:#1111">1<1/sp ansty="le--0:#D6DEEB;--1:#403F">5<3;d ivclassNa="meco">
44AEco61B0pat446<88F spans="tyle--0:#D9F5DD;--1:#11">1<111/ spans="tyle--0:#F78C6C;--1:#AA">0982<\x07 spans="tyle--0:#D9F5DD;--1:#11">1<111/ spans="tyle--0:#D6DEEB;--1:#40">3<07/>

Ambiguous Octal vs Backreference

Section titled “Ambiguous Octal vs Backreference”
AEconsB0patteAE< =sp ansty="le--0:#5CA7E4;--1:#3A68">81<1/sp ansty="le--0:#5CA7E4;--1:#3A68">8F\1<\2sp ansty="le--0:#D9F5DD;--1:#1111">1<1/sp ansty="le--0:#D6DEEB;--1:#403F">5<3;d ivclassNa="meco">
44AEco61B0pat446<88F spans="tyle--0:#D9F5DD;--1:#11">1<111/ spans="tyle--0:#F78C6C;--1:#AA">0982\x01<\x02 spans="tyle--0:#D9F5DD;--1:#11">1<111/ spans="tyle--0:#D6DEEB;--1:#40">3<02/>

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

Section titled “Options”

This rule is not configurable.

When Not To Use It

Section titled “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

Section titled “Further Reading”

Equivalents in Other Linters

Section titled “Equivalents in Other Linters”