Map vs Object: Clarifying the Differences

JavaScript offers two data structures for storing key-value pairs: Objects and Maps. While Objects have been traditionally used as Maps, the introduction of dedicated Map objects raises questions about their distinct features and purposes.

Comparison of Features

• Insertion Order: Maps preserve the insertion order of key-value pairs, while Objects do not. This allows Maps to be iterated in the same order that elements were added.
• Key Type: Maps can have keys of any type (even non-String values), whereas Objects are limited to String keys.
• Prototype: Objects have a prototype, which can introduce default keys. Maps do not have a prototype, ensuring a clean and predictable behavior.
• API: Maps provide a more comprehensive API specifically tailored for key-value operations, including methods like myMap.has(key) and myMap.size.

Benefits of Maps

• Improved Performance: Maps offer guaranteed performance across browsers for insertion order iteration, making performance more predictable.
• Enhanced Functionality: The myMap.has(key) method simplifies checks for the presence of keys, and the myMap.size property provides easy access to the number of elements in the Map.
• Specialized Behavior: Maps are optimized for key-value operations, making them more efficient for specific use cases than using Objects as Maps.