RegExp.$1, , RegExp.$9

Deprecated

Avoid using this feature in new projects. The RegExp static properties may have unintended side effects. This feature may be a candidate for removal from web standards or browsers.

: RegExp RegExp

RegExp.$1, , RegExp.$9

$1$9 RegExp RegExp.$1, RegExp.$2, RegExp

$1, , $9 RegExp RegExp undefined

RegExp 9

$1, , $9 String.prototype.replace() RegExp.$n

$n RegExp.prototype.test()

RegExp.prototype.test()

const str = "Test 24";
const number = /(\d+)/.test(str) ? RegExp.$1 : "0";
number; // "24"

re.test(str) RegExp.$n


Legacy RegExp features # additional-properties-of-the-regexp-constructor

RegExp.input ($_)
RegExp.lastMatch ($&)
RegExp.lastParen ($+)
RegExp.leftContext ($`)
RegExp.rightContext ($')

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MDN 20251110

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RegExp
1. RegExp()
1. escape()
Object/Function
1. __proto__
2. constructor