How to initialize a Map in ES6/ES2015 similar to an Object expression?

Question

What is the equivalent of

var object = {   'foo': 'bar',   1: 42 } 

using an ES6 Map?

Answer 1

The closest you can get is:

let object = new Map([   ['foo', 'bar'],   ['1', 42] ]); 

Important things to notice:

1. Object properties are identified by strings, while Map keys can be any value, so make sure all keys are strings in the input array.
2. Iterating a Map object yields entries by insertion order. That is not guaranteed for objects, so behavior might be different.

Answer 2

In modern browsers it can be as simple as:

new Map(Object.entries(object))