How Do I Copy a Map into a Duplicate Map?

With the introduction of Maps in JavaScript it's quite simple considering the constructor accepts an iterable:

var newMap = new Map(existingMap)

Documentation here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map

A simple way (to do a shallow copy) is to copy each property of the source map to the target map:

var newMap = {};
for (var i in myMap)
   newMap[i] = myMap[i];

NOTE: newMap[i] could very well be a reference to the same object as myMap[i]

Very simple to clone a map since what you're talking about is just an object. There is a Map in ES6 that you should look up, but to copy an object, just use Object.assign()

let map = {"a": 1, "b": 2}
let copy = Object.assign({}, map);

You can also use cloneDeep() from Lodash

let copy = cloneDeep(map);