# es/no-regexp-lookbehind-assertions
disallow RegExp lookbehind assertions
- ✅ The following configurations enable this rule:
plugin:es/no-new-in-es2018,plugin:es/restrict-to-es3,plugin:es/restrict-to-es5,plugin:es/restrict-to-es2015,plugin:es/restrict-to-es2016, andplugin:es/restrict-to-es2017
This rule reports ES2018 RegExp lookbehind assertions (opens new window) as errors.
# Examples
⛔ Examples of incorrect code for this rule:
/*eslint es/no-regexp-lookbehind-assertions: error */
const r1 = /(?<=a)b/
const r2 = /(?<!a)b/