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

One of the difference between Map and Object is:

Map can use complex data type as its key. like this:

const fn = function() {}
const m = new Map([[document.body, 'stackoverflow'], [fn, 'redis']]);

m.get(document.body) // 'stackoverflow'
m.get(fn) //'redis'

watch out: For complex data type, If you want to get the value, you must pass the same reference as the key.

Object, it only accept simple data type(number, string) as its key.

const a = {};
a[document.body] = 'stackoverflow';

console.log(a) //{[object HTMLBodyElement]: "stackoverflow"}