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


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.


Using the unicodeSets property


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

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


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

Browser compatibility

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See also