Map and Set are ES6 collections that provide efficient alternatives to objects and arrays. Here's how to use them effectively.
Map Basics#
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Map Keys#
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Map Iteration#
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Map vs Object#
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Set Basics#
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Set Operations#
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Set Use Cases#
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WeakMap#
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WeakSet#
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Practical Patterns#
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Converting Between Types#
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Best Practices#
Use Map When:
✓ Keys aren't strings/symbols
✓ Need to maintain insertion order
✓ Frequent additions/deletions
✓ Need map.size property
Use Set When:
✓ Need unique values only
✓ Fast membership testing
✓ Set operations needed
✓ Deduplicating arrays
Use WeakMap/WeakSet When:
✓ Keys are objects only
✓ Don't want to prevent GC
✓ Caching object metadata
✓ Private instance data
Avoid:
✗ Map for simple string keys
✗ Set for ordered unique lists
✗ WeakMap when you need iteration
✗ Converting unnecessarily
Conclusion#
Map and Set provide powerful alternatives to objects and arrays for specific use cases. Map excels with non-string keys and maintains insertion order, while Set ensures uniqueness and enables set operations. WeakMap and WeakSet are perfect for caching and tracking objects without preventing garbage collection. Choose the right collection based on your data structure needs.