RegExp.prototype.flags has a string as its value. Flags in the flags property are sorted alphabetically (from left to right, e.g. "dgimsuvy"). It actually invokes the other flag accessors (hasIndices, global, etc.) one-by-one and concatenates the results.

All built-in functions read the flags property instead of reading individual flag accessors.

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

• Polyfill of RegExp.prototype.flags in core-js
• Advanced searching with flags in the Regular expressions guide
• RegExp.prototype.source