Code Reference

Map & Set Methods

JavaScript · Methods reference

JavaScript · Methods reference

📋 Overview

ES6 collections — Map, Set, WeakMap, WeakSet.

🔧 Methods

Map

MethodDescription
set(key, value)Set value; returns map
get(key)Value or undefined
has(key) / delete(key) / clear()Membership / remove / clear
sizeEntry count (property)
keys() / values() / entries()Iterators
forEach(fn)Iterate entries

Set

MethodDescription
add(value)Add unique value
has(value) / delete(value) / clear()Membership / remove
sizeElement count
keys() / values() / entries()Values (keys same as values)
forEach(fn)Iterate values
union / intersection / difference / symmetricDifferenceSet ops (ES2024)
isSubsetOf / isSupersetOf / isDisjointFromSet relations (ES2024)

💡 Examples

See parent topic notes for runnable snippets; this page is the complete method index.

⚠️ Pitfalls

  • Mutating methods return None in Python — do not chain sort() / reverse() expecting a new list.
  • Default JS sort() compares strings — pass (a,b) => a-b for numbers.
  • SQL function names differ by dialect — verify Postgres vs MySQL docs.
  • Django QuerySet.update() skips save() signals and auto auto_now fields on models.

🔗 Related

Array Methods

JavaScript · Methods reference

Object Static Methods

JavaScript · Methods reference

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📋 Overview🔧 MethodsMapSet💡 Examples⚠️ Pitfalls🔗 Related