Symbols provide unique identifiers and enable powerful iteration patterns. Here's how to use them effectively.
Symbol Basics#
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Well-Known Symbols#
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Iterator Protocol#
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Generator-Based Iterators#
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Async Iterators#
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Custom Collection Classes#
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Symbol Use Cases#
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Built-in Iterables#
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Best Practices#
Symbols:
✓ Use for unique property keys
✓ Use Symbol.for for shared symbols
✓ Implement well-known symbols properly
✓ Document symbol purposes
Iterators:
✓ Implement Symbol.iterator for collections
✓ Use generators for cleaner code
✓ Support for...of iteration
✓ Handle cleanup in finally
Performance:
✓ Lazy evaluation with generators
✓ Avoid creating arrays when iterating
✓ Use built-in iteration methods
✓ Cache symbol references
Avoid:
✗ Using symbols for true privacy
✗ Forgetting to close iterators
✗ Infinite iterators without limits
✗ Over-engineering iteration
Conclusion#
Symbols provide guaranteed unique identifiers and enable powerful meta-programming through well-known symbols. The iterator protocol enables custom iteration with for...of, spread, and destructuring. Use generators for simpler iterator implementation and async iterators for asynchronous data streams.