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Apprentice

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Exam →Stats →Learning Path

Symbol

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Exercises (40)

○Symbol() — typeof is symbol
Beginner
○Symbol() — each Symbol is unique
Beginner
○Symbol() — description property
Beginner
○Symbol() — no description is undefined
Beginner
○Symbol() — cannot use new
Intermediate
○Symbol.for() — same key returns same Symbol
Beginner
○Symbol.for() vs Symbol() — not the same
Beginner
○Symbol.for() — typeof result
Beginner
○Symbol.for() — keyFor retrieves the key
Intermediate
○Symbol.for() — description matches key
Beginner
○Symbol.keyFor() — returns key for global symbol
Beginner
○Symbol.keyFor() — undefined for local symbol
Beginner
○Symbol.keyFor() — return type is string
Beginner
○Symbol.keyFor() — well-known symbols return undefined
Intermediate
○Symbol.keyFor() — consistent round-trip
Beginner
○Symbol.description — basic usage
Beginner
○Symbol.description — undefined when no arg
Beginner
○Symbol.description — empty string
Beginner
○Symbol.description — global symbol
Beginner
○Symbol.description — typeof is string
Beginner
○Symbol.toString() — 'Symbol(x)'
Beginner
○Symbol.toString() — no description gives 'Symbol()'
Beginner
○Symbol.toString() — includes description
Beginner
○Symbol.toString() — typeof result
Beginner
○Symbol.for().toString() — 'Symbol(key)'
Beginner
○Symbol.iterator — typeof is symbol
Beginner
○Symbol.iterator — arrays are iterable
Beginner
○Symbol.iterator — strings are iterable
Beginner
○Symbol.iterator — custom iterable object
Intermediate
○Symbol.iterator — not in global registry
Intermediate
○Symbol.toPrimitive — typeof is symbol
Beginner
○Symbol.toPrimitive — number hint
Intermediate
○Symbol.toPrimitive — string hint
Intermediate
○Symbol.toPrimitive — typeof is always symbol
Beginner
○Symbol.toPrimitive — not in global registry
Intermediate
○Symbol.hasInstance — typeof is symbol
Beginner
○Symbol.hasInstance — custom instanceof
Advanced
○Symbol.hasInstance — always a symbol
Beginner
○Symbol.hasInstance — not in global registry
Intermediate
○Symbol.hasInstance — standard instanceof still works
Beginner