Difference between “Map” and “WeakMap” in JavaScript

JavaScript “Map” and “WeakMap” objects allows you to store collection of unique keys and their corresponding values. But there are some key differences between them. Here are the differences:

• They both behave differently when a object referenced by their keys/values gets deleted. Lets take the below example code:
  var map = new Map();
  var weakmap = new WeakMap();
  
  (function(){
      var a = {x: 12};
      var b = {y: 12};
  
      map.set(a, 1);
      weakmap.set(b, 2);
  })()

  One the above self invoked function is executed there is no way we can reference {x: 12} and {y: 12} anymore. Garbage collector goes ahead and deletes the key b pointer from “WeakMap” and also removes {y: 12} from memory. But in case of “Map”, the garbage collector doesn’t remove a pointer from “Map” and also doesn’t remove {x: 12} from memory.

  So “Map” can cause more garbages in memory. We can say that “Map” references are strong pointer whereas “WeakMap” references are weak pointers.

• “WeakMap” keys cannot be primitive types. Nor they can be created by an 2D array.
  map.set(44, 12);
  
  //throws invalid type error
  weakmap.set(44, 13);
  
  //doesn't work. throws errors
  var map_1 = new WeakMap([[1, 2], [4, 5]]);
• “WeakMap” doesn’t provide any methods or functions to work with the whole set of keys. For example: size, looping etc.
  console.log(weakmap.size); //undefined
  
  
  //loop through the keys in an map
  for(var i of map)
  {
      console.log(i);
  }
  
  //loop through the keys in an weakmap doesn't work
  for(var i of weakmap)
  {
      console.log(i);
  }
  
  //delete all keys
  map.clear();
  
  weakmap.clear(); //but this works