JS Built-ins
← Symbol14 / 40
SymbolkeyForintermediate

Symbol.keyFor() — well-known symbols return undefined

📖 Usage Example
Symbol.keyFor(Symbol.iterator)    // → undefined
Symbol.keyFor(Symbol.for('x'))     // → 'x'

Well-known symbols are not in the global registry, so Symbol.keyFor returns undefined for them.

Well-Known Symbols and keyFor

Well-known symbols like Symbol.iterator are NOT in the global string-keyed registry, so Symbol.keyFor returns undefined for them.

Challenge: Verify this behaviour.

💡 Hints (1)
  • • Well-known symbols live outside the global string registry.