//using objects
let d1 = {1: "one", 2: "two"};
let d2 = {3: "three"};
let dAll = {...d1, ...d2};
//dAll is { '1': 'one', '2': 'two' }
console.log("dAll is", dAll);
//using maps (ES6 feature)
let m1 = new Map([
[ 1, "one" ],
[ 2, "two" ]])
let m2 = new Map([[3, "three"]]);
let mAll = new Map(
[...m1.entries(), ...m2.entries()]);
//mAll is { '1': 'one', '2': 'two', '3': 'three' }
console.log("mAll is", mAll);