How to merge two Maps in TypeScript

Question

I am trying to merge 2 Maps. In ES6 I would do it like so and it works perfectly fine:

const m1 = new Map();
m1.set('foo', 1);

const m2 = new Map();
m2.set('bar', 3);

const m3 = new Map([...m1, ...m2]);

If i do the same in TS i get the following an error:

Type 'Map<string, number>' is not an array type.

I assume that i have to cast it to array somehow but I did not find a working solution. How should i go about fixing this issue?

Answer 1

This works also with target ES5:

let map1:Map<string, number> = new Map([["a", 1], ["b", 2]]);
let map2:Map<string, number> = new Map([["c", 1], ["d", 2]]);

let mergedMap:Map<string, number> = new Map([...Array.from(map1.entries()), ...Array.from(map2.entries())]);