RegExp.prototype.unicodeSets

Baseline 2023

Newly available

Since September 2023, this feature works across the latest devices and browser versions. This feature might not work in older devices or browsers.

The unicodeSets accessor property of RegExp instances returns whether or not the v flag is used with this regular expression.

Try it

const regex1 = /[\p{Lowercase}&&\p{Script=Greek}]/;
const regex2 = /[\p{Lowercase}&&\p{Script=Greek}]/v;

console.log(regex1.unicodeSets);
// Expected output: false

console.log(regex2.unicodeSets);
// Expected output: true

Description

RegExp.prototype.unicodeSets has the value true if the v flag was used; otherwise, false. The v flag is an "upgrade" to the u flag that enables more Unicode-related features. ("v" is the next letter after "u" in the alphabet.) Because u and v interpret the same regex in incompatible ways, using both flags results in a SyntaxError. With the v flag, you get all features mentioned in the u flag description, plus:

The \p escape sequence can be additionally used to match properties of strings, instead of just characters.
The character class syntax is upgraded to allow intersection, union, and subtraction syntaxes, as well as matching multiple Unicode characters.
The character class complement syntax [^...] constructs a complement class instead of negating the match result, avoiding some confusing behaviors with case-insensitive matching. For more information, see Complement classes and case-insensitive matching.

Some valid u-mode regexes become invalid in v-mode. Specifically, the character class syntax is different and some characters can no longer appear literally. For more information, see v-mode character class.

Note: The v mode does not interpret grapheme clusters as single characters; they are still multiple code points. For example, /[🇺🇳]/v is still able to match "🇺".

The set accessor of unicodeSets is undefined. You cannot change this property directly.

Examples

Using the unicodeSets property

const regex = /[\p{Script_Extensions=Greek}&&\p{Letter}]/v;

console.log(regex.unicodeSets); // true

Specifications

Specification
ECMAScript® 2026 Language Specification # sec-get-regexp.prototype.unicodesets

Browser compatibility

	Desktop					Mobile						Server
	Chrome	Edge	Firefox	Opera	Safari	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet	WebView Android	Deno	Node.js
`unicodeSets`	112	112	116	98	17	112	116	75	17	23.0	112	1.32	20.0.0