JavaScript Lookbehind Assertions
Examples
Positive lookbehind assertion
Text preceding the current location must match the assertion
const RE_DOLLAR_PREFIX = /(?<=\$)foo/g
console.log("$foo %foo foo".replace(RE_DOLLAR_PREFIX, "bar")) // '$bar %foo foo'
Negative lookbehind assertion
Text preceding the current location must not match the assertion
const RE_NO_DOLLAR_PREFIX = /(?<!\$)foo/g
console.log("$foo %foo foo".replace(RE_NO_DOLLAR_PREFIX, "bar")) // '$foo %bar bar'