var map1 = new Map();
map1.set('0', 'foo');
map1.set(1, 'bar');
var iterator1 = map1.keys();
console.log(iterator1.next().value);
// expected output: "0"
console.log(iterator1.next().value);
// expected output: 1
var map1 = new Map();map1.set('0', 'foo');map1.set(1, 'bar');var iterator1 = map1.keys();console.log(iterator1.next().value);// expected output: "0"console.log(iterator1.next().value);// expected output: 1