From the docs I’ve been reading, the following ought to create an Array from the keys of a Map:

var m = new Map();
m.set("a", 1);
m.set("b", 2);

var arr1 = Array.from(m.keys());
var arr2 = Array.from(m.values());

console.log(arr1.length);
console.log(arr2.length);

I’d expect that to print 2 for both arrays, but in reality both arrays are empty and it prints 0. What gives?