Maps vs Objects in ES6, When to use?

In ES6 (ECMAScript 2015), both Map and Object can be used to store key-value pairs. However, they have distinct characteristics and use cases, and selecting the appropriate type can enhance code efficiency and maintainability.

Object

Use Cases:

• When keys are strings or symbols (Symbol).
• When methods or property inheritance is required.

Advantages:

• Simple syntax; access properties directly using dot notation (.) or bracket notation ([]).
• Highly optimized in JavaScript engines for better performance.

Disadvantages:

• Keys can only be strings or symbols, not other types.
• Does not preserve the insertion order of keys.
• Has a default prototype chain, which may include keys not part of the actual data.
• No straightforward way to retrieve the size.

Example:

javascript
let user = {
    name: "John",
    age: 30
};

console.log(user.name); // John

Map

Use Cases:

• When keys can be any value, including objects and arrays.
• When insertion order of keys is important.
• When frequently adding or removing key-value pairs is needed.

Advantages:

• Keys can be any value.
• Preserves the insertion order of keys.
• Provides a size property size.
• Optimized for operations like adding, removing, and querying keys.

Disadvantages:

• More complex syntax; requires using methods like get(), set(), and delete().
• Some older environments may not support it.

Example:

javascript
let map = new Map();
map.set(user, {age: 30});

console.log(map.get(user)); // {age: 30}
console.log(map.size); // 1

Summary

Typically, if you need a simple structure for string keys and values without concern for key order, use Object. If keys have diverse types, key order matters, or frequent addition/removal of key-value pairs is needed, recommend using Map.

In practice, the choice depends on specific requirements. For example, when building a caching system, Map is often preferred because it enables easy access and removal of data using any key type while preserving insertion order. Conversely, for a fixed configuration item, Object may be more convenient.