Useing the well-known symbol 'hasInstance' and other meta-programming

[KilianKilmister]

the projects in iter-tools that i checked ship with a is<instance>(inst) static method. Utilizing a static property Symbol.hasInstanceallows an object to be checked with the instanceof-operator which is also used by TypeScript for typechecking that way. eg:

class Instatiater {
  static [Symbol.hasInstance] (inst: any): inst is Instatiater { /* ...some check */ }
}

these projects could also benefit from other well-known symbols like Symbol.toStringTag, Symbol.isConcatSpreadable or Symbol.species (MDN-page on symbols featuring the well-known symbols)