get RegExp[@@species]

The species accessor property returns the default constructor for RegExp objects. Subclass constructors may over-ride it to change the constructor assignment.

The species property returns the default constructor function, which is the RegExp constructor for RegExp objects:

RegExp[Symbol.species]; // function RegExp()

In a derived collection object (e.g. your custom regexp MyRegExp), the MyRegExp species is the MyRegExp constructor. However, you might want to overwrite this, in order to return parent RegExp objects in your derived class methods:

class MyRegExp extends RegExp {
  // Overwrite MyRegExp species to the parent RegExp constructor
  static get [Symbol.species]() { return RegExp; }
}

• RegExp
• Symbol.species