Efficient hashmap implementations in JavaScript

While JavaScript objects can be used as dictionaries, they do not provide true hashing functionality. As a result, objects with different string representations but equivalent values may overwrite each other.

Using Custom Key Functions

To create an efficient hashmap, you can manually define a key function based on the unique characteristics of your objects. The resulting strings can then be used as keys in a regular JavaScript dictionary.

var key = function(obj){
  // Some unique object-dependent key
  return obj.totallyUniqueEmployeeIdKey; // Just an example
};

var dict = {};

dict[key(obj1)] = obj1;
dict[key(obj2)] = obj2;

Advantages of this Approach:

• Control over indexing without heavy lifting
• No overflow handling
• Can select simple or complex key functions

Avoiding Collisions

To avoid collisions between keys generated by different objects, carefully consider the unique properties of your objects and use them in your key function. If necessary, use non-Latin Unicode characters or delimiters to prevent conflicts with default properties.

ES6 Maps and Sets

ECMAScript 6 introduced Maps and Sets, which offer built-in hashing capabilities and support keys of any value, including objects.

Advantages of Maps:

• Keys can be any value, allowing objects to be hashed directly without artificial keys
• Ordered keys
• Size property for easy determination of object count
• Iterable for easy iteration