Maps vs Objects in ES6, When to use?

Question

Ref: MDN Maps

Use maps over objects when keys are unknown until run time, and when all keys are the same type and all values are the same type.

Answer 1

This question is a duplicate of but until it's closed, here's my answer from over there:

In addition to the other answers, I've found that Maps are more unwieldy and verbose to operate with than objects.

obj[key] += x
// vs.
map.set(map.get(key) + x)

This is important, because shorter code is faster to read, more directly expressive, and better kept in the programmer's head.

Another aspect: because set() returns the map, not the value, it's impossible to chain assignments.

foo = obj[key] = x;  // Does what you expect
foo = map.set(key, x)  // foo !== x; foo === map

Debugging maps is also more painful. Below, you can't actually see what keys are in the map. You'd have to write code to do that.

Objects can be evaluated by any IDE: