Q:ES6 map.keys() after map.delete(key)

Question

when I try these code:

const map=new Map([['a', 1],['b', 2],['c', 3],['d', 4],['e', 5]]);
console.log(map.keys());
map.delete('a')
console.log(map.keys());

the chrome console will show these:

MapIterator {"a", "b", "c", "d", "e"}
MapIterator {"c", "d", "e"}

"b" why not show up？

it looks like a bug to me. Interestingly, if you actually consume the iterator, There is no issue console.log([...map.keys()]); — laurent, Dec 24 '17 at 12:18
Looks like a bug to me, happens only when deleting the first key. Also `console.log(map)` prints the correct result after deletion — Shubham Khatri, Dec 24 '17 at 12:21
Yeah most probably a bug works for deleting other enteries except firstone — simbathesailor, Dec 24 '17 at 12:23
This seems to affect `map.keys()`, `map.values()` and `map.entries()` but not `map.has("b")` or `console.log(map)` — toniedzwiedz, Dec 24 '17 at 12:26

Shubham Khatri · Answer 1 · 2017-12-24T12:35:59.993

1

This is a browser compatibility issues, that happens with map.keys(), map.values(), map.entries().

The issue occurs in chrome when deleting the first key but it works when well in safari.

Also these properties don't even work in Mozilla, just returns an empty Map iterator

edited Dec 24 '17 at 12:35

answered Dec 24 '17 at 12:28

Shubham Khatri

1 Answers1